A - Z Dermatology

Words and terms related to dermatology, products, conditions and more.

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Acanthosis nigricans (AN) is a skin condition that causes one or more areas of skin to darken and thicken. Often the skin with AN feels like velvet.

People who get this skin condition sometimes mistakenly believe that a dye or something else they touched has discoloured their skin. They try scrubbing away the discolouration. Vigorous scrubbing will not get rid of AN.

Acanthosis nigricans is not contagious. It is not harmful.

Sometimes, it is a warning sign of a health problem that requires medical attention. For this reason, it is important to see a dermatologist if you notice an area of darker, thicker skin.


Acne is a skin condition that can cause one or more of the following:

  • Blackheads
  • Whiteheads
  • Pimples
  • Acne cysts or nodules (deep, painful breakouts)

Another word for pimples, or bumps that you get mostly on your face. Most acne happens when your skin makes too much oil. The oil mixes with dead skin cells and germs called bacteria to plug up the little holes in your skin called pores.


When acne breakouts penetrate the skin deeply, they damage the skin and the tissue beneath it. As the acne clears, the body tries to repair this damage. 

During the healing process, the body produces collagen—a substance that gives the skin support. If the body produces too little or too much collagen, you will see a scar. 

The type of scar depends on how much collagen your body makes.

Depressed acne scars: If the body produces too little collagen, depressions or pits form as the skin heals.

Raised acne scars: Sometimes the body produces too much collagen as it tries to heal the skin and underlying tissue. When this happens, a person develops a raised acne scar. This type of acne scar is more common in people who have skin of colour like African Americans, Hispanics, and Asians. 

Even when we do our best to prevent acne scars, some people scar. There are many treatment options, which can significantly diminish depressed and raised acne scars.


An actinic keratosis often appears as a reddish spot (as shown here) that develops on skin you seldom protected from the sun over the years.

These precancerous skin growths are common because many people seldom protect their skin from the sun with sunscreen, clothing, and shade. Without sun protection, the sun’s harmful rays can damage your skin. While your body may repair some of this damage, the sun’s rays continue to damage unprotected skin. Over the years, this damage builds up and can cause precancerous changes to your skin.


This is a disease that develops when the body attacks its own hair follicles (where hair grows from), which can cause hair loss anywhere on the body.

Many people who develop alopecia areata develop a round or oval bald patch on their scalp. The hair loss tends to be unpredictable. Hair may regrow without treatment. This happens more often when someone has a few bald patches. When the hair regrows, it may fall out again—or it may not.

If alopecia areata affects the nails, you may see dents, ridges, or brittle nails. Some people develop red nails.


Athlete's foot is a common fungal infection that most people get from walking barefoot in moist public places, like a swimming pool deck or locker room.

Despite the name, athlete’s foot can happen to anyone. It can result in flaky skin, cracking, and itchiness on the soles of the foot and between the toes.


Often called eczema or atopic eczema, this is a condition that usually develops by 5 years of age and causes extremely itchy rashes that come and go.

Atopic dermatitis (AD) is common worldwide. People of all ages from newborns to adults 65 years of age and older live with this condition. Symptoms range from excessively dry, itchy skin to painful, itchy rashes that cause sleepless nights and interfere with everyday life.


The most common type of skin cancer, basal cell carcinoma can show up on the skin in many ways.

Most people who develop this skin cancer have fair skin that they seldom protected with sunscreen or sun-protective clothing. Before they developed skin cancer, they often noticed signs of sun damage on their skin, such as age spots, patches of discoloured skin, and deep wrinkles.

Although BCC is most common in people who have fair skin, people of all colours get this skin cancer. For most people, BCC is not life-threatening. It tends to grow slowly. It seldom spreads to another part of the body. Even so, treatment is important. When found early, this skin cancer is highly treatable. An early BCC can often be removed during an appointment with your dermatologist.


Bed bugs are tiny insects that feed on human blood. They hide in dark places close to where humans sleep and usually crawl out to feed while people are fast asleep.

If you have bed bugs in your home, it's unlikely that you'll see one unless you look for them. Bed bugs hide in the crevices of mattresses, box springs, headboards, couches, and other places. They only come out to feed.

While a bed bug is feeding on you, you're unlikely to notice. Most people are asleep when they get bit. Also, before a bed bug draws your blood, it injects you with a substance that prevents you from feeling the bite. When you wake up, you may notice itchy welts.

An adult that is full of blood can be the size of an apple seed. Hungry bed bugs and younger ones are about the size of a poppy seed.


If your baby has a birthmark, you’ll likely see a spot, patch, or lump that looks different from the rest of your baby’s skin. You may see this when your baby is born. Some birthmarks appear shortly after birth.

Birthmarks come in many shapes and colours. You may see a flat or raised mark. It may the size of a pinhead or cover a large area of your child’s skin. Most birthmarks fall somewhere in between. A birthmark can be pink, red, tan, brown, or any other colour. Some look like a bruise. Others look like a stain on the skin.

Some birthmarks are common. It’s estimated that between 3% and 10% of babies are born with a type of birthmark called a hemangioma. Other birthmarks, such a port-wine stain, are less common.


Boils are pus-filled skin infections that occur around a hair follicle or oil gland. This causes a red, painful lump to form as pus collects under the skin. A boil that occurs on the eyelid is called a stye.

Most boils and styes heal on their own within one to three weeks. However, if the pain or swelling worsens after several days, another boil or stye appears, or you develop a fever or vision problems with the infection, see a board-certified dermatologist.


Dermatologists use botulinum toxin therapy to diminish signs of ageing and to treat a medical condition called hyperhidrosis (excessive sweating).


This is a rare autoimmune disease that can cause large blisters on the skin. Blisters can develop on other areas like inside the mouth, but this is rare.

Bullous pemphigoid is a chronic disease, which means it lasts longer than six weeks. For many people, this disease lasts for months or years. As older blisters open and crust over, new blisters can appear.


Cellulitis is a common and potentially serious infection caused by bacteria. The bacteria infect the deep layers of skin and tissue beneath the skin.

The first sign of cellulitis is usually red and swollen skin. When you touch the infected area, it often feels warm and tender.

This infection can show up anywhere on the skin. Adults often get it in a lower leg. In children, cellulitis tends to appear on the face or neck.


A chemical peel can diminish many signs of ageing on the face as well as the hands, neck, and chest. 

Chemical peels also treat some skin conditions. Dermatologists use chemical peels to treat some types of acne and conditions that discolour the skin. 


Chickenpox is a highly contagious disease caused by a virus. Although the incidence of chickenpox has declined significantly since the development of the chickenpox vaccine, there are still children who develop chickenpox every year. Fortunately, there is a lot parents can do at home to help ease their children’s symptoms and prevent skin infections.

The most common symptom of chickenpox is a rash that turns into itchy, fluid-filled blisters and then scabs. The rash usually shows up on the face, chest and back first and then spreads to the rest of the body.

Other signs and symptoms of chickenpox may include:

  • Fever
  • Tiredness
  • Loss of appetite
  • Headache


A cold sore is a small blister or group of blisters that usually develop on the lip or around the mouth. Cold sores are caused by the herpes simplex virus (HSV).

Cold sores are also known as fever blisters or herpes simplex labialis. The virus stays in the body after the cold sores clear. If the virus reactivates, or wakes up, you may get cold sores again.

Cold sores are generally not serious. In healthy people, cold sores tend to clear within two weeks. If you have a cold sore, you can spread the virus to others who don’t have the virus. Even when you treat cold sores, you can still spread the virus to others. You are contagious until all the sores have scabbed over.


When something that touches your skin either irritates it or causes an allergic skin reaction, you develop this skin disease. The first sign is often itchy skin, followed by a rash. You may also see blisters.

Contact dermatitis is not contagious, so you cannot give it to anyone else.

Because so many things can irritate our skin or cause an allergic skin reaction, contact dermatitis sends many people to see a dermatologist. While this may sound simple, finding the cause can be a challenge. More than 15,000 things that touch our skin can cause an allergic reaction. Some of the more common ones are fragrance and nickel, which are found in hundreds of products and everyday items. You can get a rash even if you only briefly touch something that causes an allergic reaction. This rash tends to appear hours or days after your skin touches what you’re allergic to.


Cutaneous T-cell lymphoma (CTCL) is a rare type of blood cancer.

It begins in a type of white blood cell called the T-lymphocyte (T-cell). T-cells help prevent infections and other diseases.

As odd as it sounds, most T-cells are found in our skin. That’s because our skin is the first line of defence against disease. The surface of an adult’s skin contains about 20 billion T-cells. That’s nearly twice as many T-cells as found in other parts of the body.

There are many types of CTCL. More than half the people who develop CTCL will have one of the following types:

  • Mycosis fungoides
  • Sézary syndrome


Dandruff is a common scalp condition in which small pieces of dry skin flake off of the scalp. If you have dark hair or you’re wearing dark colours, you may notice the flakes in your hair or on your shoulders. Dandruff may also make your scalp itch.

Many people believe that dandruff is caused by poor hygiene, but this is not true. Although infrequent shampooing can make dandruff more obvious, researchers are still studying the causes, which appear to be complex.

The most effective way to treat and control dandruff is to use dandruff shampoo and scalp treatments.


Dermatofibrosarcoma (dur-mah-toe-fy-bro-sar-co-ma) protuberans (pro-to-bur-anz) (DFSP) is a rare skin cancer. It begins in the middle layer of skin, the dermis. DFSP tends to grow slowly. It seldom spreads to other parts of the body.

Because DFSP rarely spreads, this cancer has a high survival rate. Treatment is important, though. Without treatment, DFSP can grow deep into the fat, muscle, and even bone. If this happens, treatment can be difficult.

The first sign of this skin cancer is often a small bump on the skin. It may resemble a deep-seated pimple or rough patch of skin. DFSP can also look like a scar. In children, it may remind you of a birthmark.


When you have diabetes, finding time for skin care can seem like a luxury. Monitoring your glucose level, sticking to a meal plan, finding time to exercise, and managing stress can definitely take priority.

Dermatologists caution that skin care also plays a key role in helping you manage diabetes. The right skin care can prevent a serious skin condition, such as an infection, open sores, or non-healing wound.


Diabetes can affect many parts of your body, including your skin. When diabetes affects the skin, it’s often a sign that your blood sugar (glucose) levels are too high. This could mean that:

  • You have undiagnosed diabetes, or pre-diabetes
  • Your treatment for diabetes needs to be adjusted


Everyone wants a happy, healthy baby; however, babies often experience discomfort from diaper rash – a condition that causes skin underneath the diaper to become red and tender. Help your baby by following dermatologists’ tips to prevent and treat diaper rash at home.


When skin loses too much water, it becomes dry. Dry skin can flake, itch, crack, and even bleed. 

With the right self-care, many people can heal dry skin at home. When effective, you tend to see improvement within 2 weeks. If you continue to have dry skin or it worsens, something other than dry air may be causing your dry skin. Excessively dry skin can develop due to:

  • An underlying medical condition, such as atopic dermatitis or kidney disease
  • Medication you take
  • What you touch throughout the day, such as certain foods
  • Age

A dermatologist can diagnose what’s causing your dry skin. If you have a condition that affects your skin, such as atopic dermatitis, your dermatologist can create a treatment plan for you. Treatment can help control the skin condition and relieve the dryness.


This type of eczema causes tiny, intensely itchy blisters on the hands or feet. It is also called pompholyx.

The blisters of dyshidrotic eczema may last for three to four weeks before clearing. Some people never develop blisters again. Dyshidrotic eczema can also be a lifelong, debilitating disease.

For most people, having dyshidrotic eczema falls somewhere in between having it once and living with a chronic, debilitating condition.

With a dermatologist’s help, many people discover what triggers their blisters. Avoiding what triggers the blisters helps to reduce flare-ups.


The word “eczema” has two meanings. It can mean either of the following:

  • A group of conditions that causes inflamed, irritated, and often itchy skin
  • Any one of the conditions within this group, such as atopic dermatitis, contact dermatitis, or stasis dermatitis.


Epidermolysis bullosa (EB) is a group of rare diseases that cause the skin to blister easily.

The skin blisters because it’s so fragile. The fragile skin is usually noticeable at birth. A hug, loving rub on the back, or diaper change can injure the skin, leading to blisters and open wounds.

Some children develop blisters in the moist tissue that lines the mouth, throat, stomach, intestines, rectum, and other areas of the body. In these areas, the friction caused by swallowing food or having a bowel movement can lead to painful blisters.

The effects that EB has on a child’s life varies considerably. Some children have a mild disease that requires taking precautions to prevent injuries. At the other end of the spectrum, EB can cause lifelong disability that needs ongoing medical care.


Is your part widening? Have you noticed that your ponytail is thinner these days? You may have female pattern hair loss (FPHL), a condition that affects millions of women. FPHL is actually the most-common cause of hair loss in women. 

For most women, FPHL begins in midlife, when a woman is in her 40s, 50s, or 60s. It can begin earlier for some women. 

FPHL is a progressive condition. This means women tend to continue losing hair. But women do not lose all of their hair, as do some men. Instead, your part often gets wider. Hair near your temples may recede. Without treatment, some women eventually develop widespread thinning.


This is a common skin infection that develops in the hair follicles. Folliculitis can appear anywhere on the skin, except for our palms and soles.

It usually looks like a sudden acne breakout. Each spot may have a red ring around it, which is a sign of the infection.

Symptoms can vary. You may not feel anything. Sometimes, the infection causes itchy skin. It’s also possible for your skin to feel painful.


The medical name for hair loss is “alopecia.” Frontal fibrosing alopecia is a specific type of hair loss. It destroys the hair follicles (openings out of which hair grows), causing permanent hair loss. With an early diagnosis and medical treatment, it’s possible to stop the disease from progressing and causing further permanent hair loss.


Genital herpes is a sexually transmitted disease (STD). It’s caused by the herpes simplex virus.

Anyone who is sexually active can catch this virus. Many people who catch the virus never know they have it because they don’t develop symptoms. They never get painful sores.

If genital sores develop, the outbreaks tend to be worse during the first year. Some people have 4 or more outbreaks within a year. In time, the outbreaks usually become less frequent. They may even stop.


Genital warts are warts that appear in the genital area. There can be one wart or a cluster of warts. People get these warts by picking up the human papillomavirus (HPV) from someone who is already infected with this virus.

HPV is a common sexually transmitted infection. It is possible to spread or get these warts even when you cannot see them.


Granuloma annulare is a skin condition that usually causes a rash. It isn’t a type of cancer. It isn’t contagious.

It rarely causes symptoms, such as pain or itch, but it can show up on your skin in different ways.

What appears on your skin depends on the type of granuloma annulare you have. The most common type causes a slightly raised patch that is ringed by a noticeable border. This patch tends to form on a hand, arm, foot, or leg, but it can appear anywhere on the skin.


One of the most common disorders that dermatologists diagnose and treat, the medical term for hair loss is alopecia.

Some people catch a contagious disease, which can lead to hair loss. For example, if you catch the fungus that causes ringworm, the fungus could grow on your scalp. Left untreated, scalp ringworm can lead to hair loss.

We lose our hair for many (with emphasis on many) reasons. Ringworm is one. A more common cause is hereditary hair loss.


Hand-foot-and-mouth disease (HFMD) is a contagious disease caused by a virus. While one of several viruses can cause it, the signs are usually the same:

  • An itchy rash on the hands, feet, or both
  • Mouth sores

You can catch HFMD from having close contact with a person who has it. You can also catch it when you touch something, such as a toy or doorknob, contaminated with a virus that causes this disease.

A child with hand-foot-and-mouth disease can often experience painful mouth sores that last for 7 to 10 days.

While many people worry that they can get HFMD from a pet or other animal, you cannot. Animals cannot get HFMD.


The medical name for head lice is Pediculus humanus capitis

Having head lice does not mean you are dirty. Most people get head lice when they have head-to-head contact with someone who has head lice. Head-to-head contact lets the lice crawl from one head to another head. The lice do not care whether the person has squeaky-clean hair or dirty hair. The lice are looking for human blood, which they need to survive.

Millions of people get head lice each year. Head-lice infestations are especially common in schools.


Warning signs can appear on your skin and nails, which is why your dermatologist may be the first doctor to notice that you have heart disease. If you know what to look for, you can also find warning signs of heart disease on your skin and nails.


Herpes simplex is a common viral infection. If you’ve ever had a cold sore or fever blister, you picked up the herpes simplex virus. Most cold sores are caused by herpes simplex virus type 1 (HSV-1).

  • Oral herpes
  • Mouth herpes
  • Herpes simplex labialis

After clearing, herpes simplex sores can return. When the sores return, the outbreak tends to be milder than the first outbreak.

A closely related herpes simplex virus, HSV-2, causes most cases of genital herpes. But either HSV-1 or HSV-2 can cause a herpes sore on the face or genitals.


Hidradenitis suppurativa (HS) is a little-known disease that causes deep and painful lumps under the skin, usually in the armpits or groin.

Many people mistake the deep lumps for painful pimples or acne cysts. HS can also be misdiagnosed as boils, infected hair follicles (folliculitis), or a sexually transmitted disease.


This is a skin reaction that causes bumps, raised patches, or both to suddenly appear on the skin. The bumps and raised patches are often itchy and may look swollen. The medical name for hives is urticaria.

This is a skin reaction that causes bumps, raised patches, or both to suddenly appear on the skin. The bumps and raised patches are often itchy and may look swollen. The medical name for hives is urticaria.

Are hives contagious? No, you cannot get hives by touching someone else’s hives or being around someone who has hives.

However, some people develop hives when they have a contagious disease like strep throat or a common cold. If someone with hives has a contagious disease, you can catch the contagious disease — but not hives.


This is a medical condition that causes excessive sweating. The word “hyperhidrosis” (hi-purr-hi-DROE-sis) means too much (hyper) sweating (hidrosis).

Excessive sweating happens when a person sweats more than is necessary. Yes, it’s necessary to sweat. Sweating cools the body, which prevents us from overheating. People who have hyperhidrosis, however, sweat when the body does not need cooling.

Many people who have hyperhidrosis sweat from one or two areas of the body. Most often, they sweat from their palms, feet, underarms, or head. While the rest of the body remains dry, one or two areas may drip with sweat.


Ichthyosis is a group of skin diseases that causes extremely dry, thick, and scaly skin. The skin often looks like it has fish scales.

There are more than 20 different types of ichthyosis. The most common type is ichthyosis vulgaris. About 95% of people who develop ichthyosis get this type.

The other types are rare and include harlequin ichthyosis, lamellar type, and x-linked ichthyosis.

Of all the types, ichthyosis vulgaris is the mildest. It often begins in childhood.


Imiquimod (ih-mih-kwih-mod) is a prescription medicine that you use at home. It comes in a cream that you apply to your skin. 

 Your dermatologist may prescribe imiquimod to treat:

  • Actinic keratosis (AK)
  • Basal cell carcinoma (the earliest form of this skin cancer)
  • Genital warts


Also called school sores

Impetigo is a common skin infection, especially in children. It is caused by a bacteria. It’s also highly contagious.

Most people get impetigo through skin-to-skin contact with someone who has it. Children and athletes like wrestlers and football players often get it this way. Blisters and crusts are common signs of impetigo.


Isotretinoin (eye-soh-tret-in-OH-in) is a prescription medication for severe acne. This type of acne causes deep, painful cysts and nodules, which can be the size of a pencil eraser or larger. As this acne clears, scars often appear.

Severe acne can be difficult to treat. When other treatments fail to clear the skin, isotretinoin may be an option. Treatment with isotretinoin often results in prolonged clearance of acne, which can be permanent for some patients.


A keloid is a type of raised scar. Unlike other raised scars, keloids grow much larger than the wound that caused the scar.

Not everyone who gets a scar will develop a keloid. If you have keloid-prone skin, however, anything that can cause a scar may lead to a keloid. This includes a cut, burn, or severe acne. Some people see a keloid after they pierce their ears or get a tattoo. A keloid can also form as chickenpox clear. Sometimes, a surgical scar becomes a keloid.


Keratosis pilaris is a common skin condition, which appears as tiny bumps on the skin. Some people say these bumps look like goosebumps or the skin of a plucked chicken. Others mistake the bumps for small pimples.

These rough-feeling bumps are actually plugs of dead skin cells. The plugs appear most often on the upper arms and thighs (front). Children may have these bumps on their cheeks.


Kidney doctors, called nephrologists, often care for patients with kidney disease. When a kidney disease affects the skin, a nephrologist may team up with a dermatologist. Some skin conditions that develop due to kidney disease can be difficult to control.

For example, if a patient has extremely itchy skin, it may be impossible to sleep through the night. A board-certified dermatologist can help a patient get some relief. This may involve using the right balance of moisturisers and medication that you apply to the skin. Some patients get relief with a treatment called UVB phototherapy.


When it comes to the use of laser technology in skin care, the future is now. Concepts that were once reserved for science fiction stories have catapulted skin care into a new age. Many of these innovations include the use of laser technology to treat myriad conditions that range from removing pre-cancerous skin growths to reducing wrinkles.


Leprosy, also called Hansen’s disease, is a contagious disease. One way it spreads is from person to person. Even so, it’s actually hard to catch. According to the Centres for Disease Control and Prevention (CDC), about 95% of humans are immune to the bacteria that cause this disease1.

Scientists have learned that to catch leprosy, a healthy person must have months of close contact with someone who has leprosy. It’s believed that the disease spreads when a person who has leprosy coughs or sneezes. When a healthy person repeatedly breathes in the infected droplets, this may spread the disease.

You can also get leprosy from an armadillo. It’s possible to catch the disease by handling an armadillo or spending time in an area where these animals live.


Many people get lichen planus. This disease can develop on one or several parts of the body. It can appear on the skin or inside the mouth. Sometimes, it appears in both places. Lichen planus can even change the way a person’s fingernails or toenails look. It also can appear on the genitals or a person’s scalp.

On the skin, lichen planus often causes bumps that are shiny, firm, and reddish purple. Sometimes the bumps have tiny white lines running through them. These lines are called Wickham’s striae.


Lupus is a disease that can affect the skin in many ways. It may cause a:

  • Widespread rash on the back
  • Thick scaly patch on the face
  • Sore(s) in the mouth or nose
  • Flare-up that looks like sunburn
  • Butterfly rash - This rash appears on the nose and cheeks in the shape of a butterfly, skipping the skin under each side of the nose.

When lupus affects the skin, it is called cutaneous (medical term for skin) lupus. There are different types of cutaneous lupus. For many people who have cutaneous lupus, the lupus affects only their skin.

Some types of cutaneous lupus are more common in people who have systemic lupus erythematosus (SLE). SLE is a type of lupus that can affect different parts of the body, including the skin, joints, and lungs.


Lyme disease is caused by a bite from a black-legged tick. If you are bitten by this tick and develop Lyme disease, you may see a bull’s-eye rash. It’s a common sign of Lyme disease, but it’s not the only sign. Lyme disease occurs in stages. 


Melanoma, the most serious form of skin cancer, is characterised by the uncontrolled growth of pigment-producing cells. Melanomas may appear on the skin suddenly without warning but also can develop within an existing mole. The overall incidence of melanoma continues to rise.

Melanoma is a skin cancer that can show up on the skin in many ways. It can look like a:

  • Changing mole
  • Spot that looks like a new mole, freckle, or age spot, but it looks different from the others on your skin
  • Spot that has a jagged border, more than one color, and is growing
  • Dome-shaped growth that feels firm and may look like a sore, which may bleed
  • Dark-brown or black vertical line beneath a fingernail or toenail
  • Band of darker skin around a fingernail or toenail
  • Slowly growing patch of thick skin that looks like a scar

Melanoma can spread quickly. Found early, this skin cancer is highly treatable. Once melanoma spreads, treatment becomes more difficult.


Melasma is most common in women. Many women first see these blotchy patches and freckle-like spots on their face during pregnancy or when they start taking birth control pills. Melasma is so common during pregnancy that it’s sometimes called the “mask of pregnancy.” For some women, the melasma goes away after their baby is born or they stop taking birth control pills.

Women who have medium to dark skin tones are most likely to develop melasma. When melasma appears, it can cause tan, brown, greyish brown, or bluish grey patches and freckle-like spots. These usually appear on certain areas of face like the cheeks, forehead, chin, and even above the upper lip. While less common, melasma can develop on the arms, neck, or elsewhere.


Merkel cell carcinoma (MCC) is a rare skin cancer.

While MCC is rare, the cancer records also indicate that more people are developing this skin cancer than ever before.

Dermatologists believe that more Americans are developing (and will develop) MCC than ever before because:

  • A growing number of people in the United States are now 65 years of age or older, and this number is expected to rise.
  • Many people who are 65 or older seldom protected their skin from the sun.

Research shows that nearly everyone who develops MCC is 50 years of age or older. Most of them also have fair skin and seldom protected their skin from the sun.


Also called nevi. Moles are common. Almost every adult has a few of them. Adults who have light skin often have more moles. They may have 10 to 40 moles on their skin. This is normal.

Most moles appear on the skin during childhood and adolescence. Moles will grow as the child (or teen) grows. Some moles will darken, and others will lighten. These changes are expected and seldom a sign of melanoma, the most-serious skin cancer.

For adults, new moles and changes to existing moles can be a sign of melanoma. Caught early, melanoma is highly treatable. Here are three facts that can help you find melanoma early and get treatment:

  • A change to a mole or a new mole is often the first sign of melanoma
  • You can find melanoma early by checking your own skin
  • If you see a mole or other spot that's growing, itching, bleeding, or changing in any way, immediately make an appointment to see a dermatologist


Caused by a virus, molluscum contagiosum causes small bumps on the skin that tend to clear with time. While molluscum contagiosum may sound like a dreaded spell from a Harry Potter story, it’s actually a skin condition that’s relatively harmless.

You can get molluscum at any age, but it’s most common in children who are 1 to 10 years old. Children who have atopic dermatitis (often called eczema) tend to get it more easily. As the name suggests, molluscum is contagious.


It’s easy to get a fungal nail infection. If you have a fungal infection on your foot, the fungus can spread to one or more of your nails. This is quite common.

You can also catch a fungal nail infection in a warm, moist place such as a pool deck or locker room. If someone else has a fungal infection and walked barefoot there, all you have to do is walk barefoot in the same area.

Having wet nails for a long time can also lead to nail fungus. Some people develop it when they wear the same pair of sweaty shoes or boots every day. Fingernails that are wet for hours at a time due to a job or hobby are also susceptible.

What you see on infected nails will vary with the type of fungus causing the infection.


Neurodermatitis is a type of eczema that begins with an itch. Most people develop one or two itchy patches. Another name for this skin condition is lichen simplex chronicus. You cannot catch neurodermatitis from someone. You cannot give anyone neurodermatitis.

Scratching the itchy patch of skin is what causes the rash. This itchy patch often develops on an arm, leg, back of the neck, scalp, or groin area. When it begins in the groin area, it tends to develop on the anus, scrotum, or vulva.

While this patch can be intensely itchy, the itch tends to come and go. Many people say that the patches feel the itchiest when they are relaxing. It’s common for the itch to be most intense right before falling asleep.

Without treatment, the itch can worsen. Some people say the itch wakes them from a sound sleep. If this happens often, the loss of sleep can affect your quality of life.


Nickel is one of the most common causes of allergic contact dermatitis: a skin rash or irritation caused by touching an allergen. In fact, it is estimated that more than 18 percent of people in North America are allergic to nickel, including 11 million children in the U.S.

If you have a nickel allergy, the best way to avoid symptoms is to avoid objects containing nickel. However, this can be challenging, since nickel is present in many common household items.


Like other types of eczema, nummular eczema is very itchy. It causes itchy, raised, and round to oval spots on the skin that can grow together to form large, slightly raised patches.

This type of eczema tends to:

  • Develop on extremely dry skin
  • Appear after an injury like a cut, bug bite, or scrape
  • Be more common in people who already have one of these eczemas: atopic dermatitis, stasis dermatitis, or contact dermatitis

When caught early and treated properly, nummular eczema can heal within 3 to 4 weeks.


People who have rosacea are often unaware that it can also develop in their eyes. As a result, symptoms, such as irritated or dry eyes, are often overlooked. In fact, many people mistakenly believe that something else, such as allergies or contact lenses, is causing their eye problems.

One of the benefits of seeing a dermatologist for rosacea and keeping all of your follow-up appointments is that you can catch eye problems early. More than half of all people who have rosacea will develop symptoms in their eyes at some point.

The medical name for this condition is ocular rosacea


Pemphigus is a group of rare diseases that causes blisters. There are many different types of pemphigus, including:

  • Pemphigus vulgaris
  • Pemphigus foliaceus
  • Drug-induced pemphigus
  • Fogo selvagem
  • Paraneoplastic pemphigus

Regardless of type, the blisters are soft, limp, and break open easily. Without treatment, the blisters and painful sores can become widespread.

Most people get blisters on their skin. With some types of pemphigus, blisters form inside the mouth. A few types cause blisters on moist tissues like those that line the inside of the nose and eyes, throat, anus, or genitals.

Anywhere the blisters form, they tend to break open quickly, leaving painful sores. In the throat, the sores can cause hoarseness. Mouth sores can make eating, drinking, and talking difficult. When sores develop, they tend to heal slowly. Some may never heal.


If you have a rash around your mouth, you may have perioral dermatitis. This rash often looks like small, red, acne-like breakouts in people with light-coloured skin and skin-coloured breakouts in people who have skin of colour.

Whether red or skin coloured, this rash can itch. Sometimes, the rash causes a burning sensation. It’s also possible that you won’t have any itching or burning. You’ll likely have dry and flaky skin where you have the rash, though.


This condition causes a rash that will clear on its own. The first sign of this rash is often a large oval patch on the skin, which is followed by many smaller patches or tiny bumps.

While more than one person in a household may have this rash at the same time and outbreaks can occur, pityriasis rosea is not thought to be contagious.


Poison ivy, oak, and sumac all contain an oil called urushiol (yur-oo-shee-aal). If you have an allergic reaction to this oil, you can develop a rash. Because most people are allergic to this oil, just about everyone who comes into contact with it develops a rash.

While rare, some people see black spots instead of a red rash on their skin. These spots look like black lacquer spilled onto the skin. Instead of black spots, some people develop black streaks on their skin.

If you develop black spots or streaks, there tends to be little or no redness and swelling. The medical term for this condition is black-spot poison-ivy dermatitis.


This is a skin disease that usually begins with intensely itchy skin. Scratching and rubbing the itchy skin cause hard, itchy bumps to appear on the skin.

Before you see the bumps of prurigo nodularis, the skin is often intensely itchy. You may have one or two small areas of itchy skin, or the itch may be widespread. The itch may come in short, intense bursts or be present most of the time.

When the skin itches, it causes an uncontrollable urge to scratch and rub. After about six weeks, hard bumps called nodules appear where you’ve been scratching and rubbing.

The bumps are also intensely itchy. The frequent scratching can cause scrapes and tears on the skin. Some people scratch until the itchy bumps break open and bleed or the skin feels too painful to touch. The open and injured skin can become infected.


Psoriasis (suh-rye-ah-sis) is a condition that causes the body to make new skin cells in days rather than weeks. As these cells pile up on the surface of the skin, you may see thick, scaly patches.

Plaque psoriasis is the most common type of psoriasis. Those thick, scaly patches that develop on the skin are called plaques (placks). When someone has plaque psoriasis, you’ll often see raised patches coated with a silvery-white scale.

Plaques can appear anywhere on the skin, but you’re most likely to find them on the:

  • Knees
  • Elbows
  • Lower back
  • Scalp

Plaques tend to vary in size. They may appear on the skin as a single patch or join together to cover a large area of skin. No matter the size, plaques tend to be itchy. Without treatment, the itch can become intense. Some people notice that their skin stings, burns, or feels painful and tight. Most people who get psoriasis have it for life. 


Do you have psoriasis? If so, it's important to pay attention to your joints. Some people who have psoriasis get a type of arthritis called psoriatic arthritis. 

This arthritis often begins with a few swollen joints. A single finger or toe may be noticeably swollen. Some people feel stiff when they wake up. As they move around, the stiffness fades.

Most people get psoriatic arthritis about 5 to 12 years after psoriasis. This arthritis can show up earlier. Some people get psoriatic arthritis and psoriasis at the same time. A few get psoriatic arthritis first and psoriasis later.

If you have psoriasis, there is no way to tell whether you will get psoriatic arthritis. This is why it is important to pay attention to swollen joints. An early diagnosis and treatment will help. These can reduce the effect that arthritis has on your life.


If you have ringworm, you may think you have worms in your skin or a disease caused by worms. You have neither. Ringworm is actually a skin infection caused by fungus. No worms involved.

The name “ringworm” probably comes from the rash that many people see. On the skin, the rash often has a ring-shaped pattern and a raised, scaly border that snakes its way around the edge like a worm.Ringworm is common. You’ve already had it if you had:

  • Athlete’s foot
  • Jock itch
  • Scalp ringworm

Ringworm can appear on just about any part of your body. On the palms, soles, scalp, groin, and nails, the rash lacks the ring-shaped pattern. On the soles and groin, ringworm also has a different name.

No matter where ringworm appears on the body, treatment is important. Without treatment, the rash tends to grow slowly and cover a larger area. You can also infect other areas of your body. Treatment can get rid of the ringworm and stop the itch, which can be intense. Because ringworm is contagious, treatment can also prevent you from spreading it to others.


Rosacea (rose-AY-sha) is a common skin disease. It often begins with a tendency to blush or flush more easily than other people. The redness can slowly spread beyond the nose and cheeks to the forehead and chin. Even the ears, chest, and back can be red all the time.

Rosacea can cause more than redness. There are so many signs and symptoms that rosacea has four subtypes.

  • Erythematotelangiectatic rosacea
  • Papulopustular rosacea
  • Phymatous rosacea
  • Ocular rosacea

With time, people who have rosacea often see permanent redness in the centre of their face.


Sarcoidosis is a disease that causes abnormal masses or growths called granulomas. A granuloma isn’t a type of cancer. It’s a cluster of inflamed cells.

When someone has sarcoidosis, granulomas can develop in the skin, inside the body, or both. The most common places for granulomas to develop are the lungs, lymph nodes, and skin.

For some people, sarcoidosis develops in one place, such as the skin. Sarcoidosis can also develop in more than one part of the body. For example, it could be found in the lungs and skin. It’s also possible for granulomas to develop in one place, clear, and then appear in another part of the body later.


A mite causes this common skin condition. Called the human itch mite, this eight-legged bug is so small that you cannot see it on the skin. People get scabies when the mite burrows into the top layer of skin to live and feed. When the skin reacts to the mite, an extremely itchy rash develops.

This mite can travel from the infected person to another person. Most people get scabies from direct, skin-to-skin contact. Less often, people pick up mites from infested items such as bedding, clothes, and furniture. The mite can survive for about three to four days without being on a human. Worldwide, there are millions of cases of scabies each year.

Anyone can get scabies. It strikes people of all ages, races, and income levels. People who are very clean and neat can get scabies. It tends to spread easily in nursing homes and extended-care facilities. The good news is that a dermatologist can successfully diagnose and treat scabies. With today’s treatments, scabies need only cause short-term distress.


Psoriasis (sore-EYE-ah-sis) can appear anywhere on the skin. When it forms on the scalp, it is often called scalp psoriasis.

Scalp psoriasis can extend beyond the scalp. It can appear on the forehead. Sometimes, it extends to the back of the neck or appears behind the ears. On the scalp, psoriasis may need different treatment. The skin on the scalp is thicker. Hair can get in the way. 


When you injure your skin, your body naturally repairs the damage. How your body repairs this damage depends on how deeply the injury penetrates your skin.

If the injury damages the top layer of your skin, you’ll likely see new skin when the wound heals. To repair damage that goes deeper than the first layer, your body makes a tissue that’s thicker than your skin. This thicker tissue often becomes a scar. New scars have a pink to reddish colour. As a scar matures, it often turns lighter or darker than your skin. Most scars are flat, and the skin on top tends to look wrinkled.

If your body makes lots of extra tissue, you’ll see a raised scar. Sometimes, the body makes an excessive amount of extra tissue and you see a raised scar that is bigger than the original wound. This type of raised scar is called a keloid. You may see a sunken scar if something causes a lot of inflammation in your skin, such as acne or chickenpox. This happens because the inflammation destroys collagen in your skin. This type of scar tends to appear when acne or chickenpox heals.


When a person has scleroderma, the body makes too much collagen. This excess collagen, the substance that holds our body together, causes hardening and tightening.

Most people have hardening and tightening on their skin. Scleroderma means “hard skin.” But this disease can affect more than the skin. Joints, muscles, and even internal organs like the kidneys and lungs can harden and tighten.

Many people who have scleroderma lead normal—or almost normal—lives. Where you have the hardening and tightening varies with the type of scleroderma you have. When scleroderma affects the skin and sometimes the underlying tissue, a person has localised scleroderma.


Also called sebaceous gland carcinoma, sebaceous gland adenocarcinoma, or meibomian gland carcinoma.

Sebaceous (suh-bey-shuhs) carcinoma (SC) is a rare skin cancer. It is considered an aggressive skin cancer because it can spread. Found early and treated, treatment is often successful. It is helpful to know that:

  • Most SCs begin on an eyelid.
  • You may notice a painless, round, firmly implanted tumor on your upper or lower eyelid.
  • Sometimes you have to pull gently on your eyelid to see the tumor.

This cancer may begin elsewhere. It can develop in any sebaceous gland. We have sebaceous glands on most areas of our skin. SC tends to develop in and around the eyes because we have the greatest number of sebaceous glands in that area.


This is a very common skin disease that causes a rash. The skin tends to have a:

  • Reddish color
  • Swollen and greasy appearance
  • White or yellowish crusty scale on the surface

One or more of these rashes can appear on the body. Sometimes, the affected skin itches.

Many infants get cradle cap. This is a type of seborrheic dermatitis that develops in babies. Scaly, greasy patches form on the baby’s scalp. The patches can become thick and crusty, but cradle cap is harmless. Cradle cap usually goes away on its own within a few months.


Seborrheic keratosis is a common skin growth. It may seem worrisome because it can look like a wart, pre-cancerous skin growth (actinic keratosis), or skin cancer. Despite their appearance, seborrheic keratoses are harmless.

Most people get these growths when they are middle aged or older. Because they begin at a later age and can have a wart-like appearance, seborrheic keratoses are often called the “barnacles of aging.”

It’s possible to have just one of these growths, but most people develop several. Some growths may have a warty surface while others look like dabs of warm, brown candle wax on the skin.


Most people who get this disease develop a painful, blistering rash. Is it contagious? Yes, but you cannot give anyone shingles. While you have blisters, you can spread a virus. If that virus infects someone who hasn't had chickenpox (or the chickenpox vaccine), the person can get chickenpox.

A virus causes shingles. It’s the same virus that causes chickenpox. In fact, to get shingles, you must have the chickenpox virus inside your body. Anyone who has had chickenpox has this virus. After you recover from chickenpox, the virus moves to nerves inside your body, where it goes to sleep. You will always have the virus inside your body. If the virus wakes up, you get shingles.

Many people mistakenly believe that they cannot get shingles because they don’t remember having chickenpox.


The word “biopsy” is one of those worrisome words that people often associate with cancer. While it’s true that your dermatologist will perform a skin biopsy if a growth on your skin might be skin cancer, this medical procedure helps dermatologists diagnose many different skin conditions.

If your dermatologist thinks you need a skin biopsy, they can perform this procedure during an office visit while you remain awake.

During a skin biopsy, your dermatologist removes a small amount of skin, which will be looked at under a microscope. This magnified view is the only way to diagnose some skin diseases, including skin cancer, infections, and conditions that cause blisters. A skin biopsy may also be used to find out what’s causing a rash.


It’s an abnormal growth of skin cells, which is usually caused by the sun’s harmful rays. Caught early, skin cancer is highly treatable.

The type of skin cancer a person gets is determined by where the cancer begins. If the cancer begins in skin cells called basal cells, the person has basal cell skin cancer. When cells that give our skin its color become cancerous, melanoma develops.

  • Basal cell carcinoma (BCC)
  • Squamous cell carcinoma (SCC) of the skin
  • SCC can develop from a precancerous skin growth
  • Melanoma
  • Cutaneous T-cell lymphoma.
  • Dermatofibrosarcoma protuberans (DFSP)
  • Merkel cell carcinoma
  • Sebaceous carcinoma


A common type of skin cancer, squamous cell skin cancer can develop from a pre-cancerous skin growth called an actinic keratosis (AK).

Squamous cells are found throughout the human body. These cells line organs, such as the lungs, throat, and thyroid. We also have squamous cells in our skin. The job of squamous cells is to protect what lies beneath. In our skin, these cells sit near the surface, protecting the tissue beneath.

Anywhere we have squamous cells, we can develop a type of cancer called squamous cell carcinoma (SCC). In the skin, this cancer is usually not life-threatening. It tends to grow slowly, but it can grow deep. When the cancer grows deep, it can injure nerves, blood vessels, and anything else in its path. As the cancer cells pile up, a large tumour can form.

Most people who develop this skin cancer have fair skin that they seldom protected with sunscreen or sun-protective clothing. Before developing this skin cancer, they tend to notice signs of sun damage on their skin, such as age spots, patches of discoloured skin, and deep wrinkles.


This is a common type of eczema that develops in people who have poor blood flow. Because poor blood flow usually develops in the lower legs, stasis dermatitis often appears near your ankles.

Early signs of stasis dermatitis - swelling and faintly discoloured skin, especially over varicose (enlarged, bulging) veins, are often the first signs of this disease.

Stasis dermatitis can occur in other areas of the body aside from the lower legs, but that’s rare. You may know of stasis dermatitis by another name. It’s also called gravitational dermatitis, venous eczema, or varicose eczema.


A stretch mark is a type of scar that develops when our skin stretches or shrinks quickly. The abrupt change causes the collagen and elastin, which support our skin, to rupture. As the skin heals, stretch marks may appear.

Not everyone develops these narrow bands on their skin. Fluctuating hormone levels seem to play a role. You may also have a higher risk if people in your family get stretch marks.

If you develop stretch marks, you’re most likely to do so during these times:

  • Growth spurts that happen in puberty
  • Pregnancy
  • Rapid weight loss or gain
  • Weight training when you have rapid muscle growth

Applying a corticosteroid to your skin for a long time can also cause stretch marks. If you have Cushing’s disease or Marfan syndrome, you may see stretch marks.

When stretch marks first appear, they tend to be red, purple, pink, reddish-brown, or dark brown, depending on your skin colour. Early stretch marks may feel slightly raised and can be itchy. In time, the colour fades and the narrow bands sink beneath your skin. If you run your finger over a mature stretch mark, you often feel a slight depression.


Syphilis is caused by a bacterial infection. Most people become infected during sex. Without treatment, syphilis can progress through stages and can cause serious health problems.

For many years, syphilis was thought to be a disease of the past. Now, it’s making a comeback. In 2018, more people were diagnosed with syphilis than HIV. The good news is that syphilis is easy to diagnose and cure. Usually, a simple blood test tells you if you have syphilis and an antibiotic medication cures it.

Syphilis can cause problems on the skin and in nearly every organ inside the body. The earliest warning signs are often on the skin. The primary stage of syphilis begins 10 to 90 days after you become infected. Most people develop symptoms about 3 weeks after having sex with someone who has syphilis.

What you may notice: During this stage, you may have:

  • One or more open sores called chancres, which often feel firm and painless
  • Swollen lymph nodes


Although your thyroid gland sits deep in your neck, your dermatologist may be the first doctor to notice signs of thyroid disease. That’s because many signs and symptoms of thyroid disease develop on the skin, hair, and nails.


Also called pityriasis versicolor

We all have yeast living on our skin. When yeast grows out of control, a person can get a skin disease called tinea versicolor. Your dermatologist may tell you that you have a fungal infection on your skin. Yeast is a type of fungus.

Many people get tinea versicolor. It is one of the most common skin diseases in tropical and subtropical areas of the world. People who live in tropical areas may have tinea versicolor year-round.


Vitiligo (vit-uh-lie-go) causes the skin to lose its natural colour. Patches of lighter skin appear. Some people develop a few patches. Others lose much more skin colour.

Vitiligo can also affect other parts of your body. A section of hair can turn white. Some people lose colour inside their mouths. Even an eye can lose some of its color. What causes this color loss is still a mystery. We do know that vitiligo is not contagious. It is not life-threatening.

But vitiligo can be life-altering. Some people develop low self-esteem. They may no longer want to hang out with friends. They can develop serious depression. Most people have vitiligo for life, so it’s important to develop coping strategies. A coping strategy that helps many people is to learn about vitiligo. Another helpful strategy is to connect with others who have vitiligo.


Warts are benign (not cancerous) skin growths that appear when a virus infects the top layer of the skin. Viruses that cause warts are called human papillomavirus (HPV). You are more likely to get one of these viruses if you cut or damage your skin in some way.

Wart viruses are contagious. Warts can spread by contact with the wart or something that touched the wart.

Warts are often coloured and feel rough, but they can be dark (brown or grey-black), flat, and smooth.


Everyone has sun-sensitive skin. It’s the reason we tan and sunburn. It’s why freckles, age spots, and skin cancers appear.

Some people are born more sun sensitive than others. People who have an extreme sensitivity to sunlight are born with a rare disease known as xeroderma pigmentosum (XP). They must take extreme measures to protect their skin from ultraviolet (UV) light. Anything that emits UV light, including the sun and some lightbulbs, can damage their skin.

When people with XP go outdoors during daylight, they need to cover up. Dermatologists recommend that they wear clothing which offers maximum protection from UV light. To protect their face and eyes, they should put on UV-protective sunglasses, goggles, or a face shield. Beneath this outer protective layer, they have on sunscreen, which is necessary should any skin become uncovered.

Text reference: https://www.aad.org/public/diseases/a-z