Types of Skin Lesions and Their Causes

A man's back with moles and freckles

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Sensitive Content: Medical Images Included

This article contains medical images of skin lesions.

Chances are, you’ve had a skin lesion. While many skin lesions are harmless and go away on their own, other skin lesions can be dangerous if not treated.

What Is a Skin Lesion?

A skin lesion is an abnormal change to the skin—an area of skin that’s different from the surrounding skin. A lesion can be a bump, ulcer, sore, or discolored area. Skin lesions can be smooth or textured, symmetric or irregularly shaped, large or small, and benign or cancerous. Some lesions might cause itchiness or pain, while others might not be bothersome at all. 

Primary vs Secondary Skin Lesions

Skin lesions are generally classified into two categories:

Primary skin lesions are skin abnormalities that can be present from birth or that develop later in life. Examples include birthmarks, moles, and acne. 

Secondary skin lesions are the result of an irritated primary skin lesion. An example could be a mole that you scratched that has since bled and crusted over.

Types of Primary Skin Lesions

Whether the result of genetics or an environmental trigger, there are many types of primary skin lesions. 

Macules

Macules are flat lesions that are usually less than 1cm in size. They’re typically the same height as the rest of the skin but can be a different shade—like brown, white, red, or tan. Macules include: 

Freckles

A close-up on arm with freckles

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Sun exposure prompts the production of more melanin (pigment). That can cause small, flat brown dots on the skin called freckles. Freckles are typically harmless and don’t require treatment. 

Moles

Moles on a man's back

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Bigger than freckles, flat moles develop when the skin’s pigment cells grow together. Moles can be brown, tan, or pink in shade, depending on your skin tone. Common moles are round or oval, have a smooth texture, have a defined border, and can be dome-shaped. It’s unlikely that a common mole would turn into melanoma (the deadliest form of skin cancer). It would be atypical moles—meaning they are unusual because they don’t fit the description of a common mole—that may be cancerous.

Dark Spots

A women with dark spots.

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Also known as post-inflammatory hyperpigmentation, dark spots can develop after an acne breakout clears up, after you use certain medications, or as you go through hormonal changes. They tend to be common among people with darker skin tones due to the skin’s melanin (pigmentation) production process. Dark spots are treatable but can return without continued treatment, such as not wearing sunblock. 

Blisters

These little bubbles of liquid that form near the top layers of the skin typically develop when there’s repeated friction against a certain part of the skin—like when your shoes rub against your heel—or in response to heat or skin condition. Blisters include: 

Vesicles

A close-up of vesicles on the skin

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Usually no larger than 1cm, tiny fluid-filled blisters known as vesicles may develop in a rash-like formation—often alongside allergic reactions, health conditions, or infections. Vesicles may require treatment depending on their underlying cause.

Bullae

Large blisters on a man's hand

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Bullae are larger fluid-filled blisters that are typically bigger than 1cm. Caused by friction, infection, or inflammation, bullae can be filled with clear fluid or blood. They tend to go away on their own. 

Papules

These raised, solid skin lesions can grow up to 1cm in size. Papules include: 

Warts

A wart on a person's finger

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Warts are small, flat, noncancerous growths that develop when the human papillomavirus (HPV) comes into contact with the skin. Where the warts develop depend on the HPV strain, most commonly developing on the hands, feet, and genital area. Warts may go away on their own, but a healthcare provider can remove them if needed.

Acne Papule

Close-up of a red pimple

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This common type of acne pimple describes small, hard, inflamed (and sometimes red) bumps that develop on the skin. The pimple can pop up thanks to acne-producing factors like excess oil, bacteria, and dead skin cells. 

Actinic Keratosis

Actinic keratosis scabs

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Actinic keratosis is the most common precancerous skin growth that develops as a result of repeated sun exposure. These scaly papules are rough-feeling and can be brown, tan, white, red, pink, or skin-colored. They often itch and scab over.

Plaques

Plaques are rough-textured, raised lesions that are bigger than 1cm, including:

Psoriasis Plaques

Psoriasis plaques on a person's knees

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These plaques develop with the skin condition psoriasis. Psoriasis is characterized by these plaques, which are thick, silvery patches that often show up on the elbows, knees, scalp, and lower back.

Nodules

Raised, solid, or fluid-filled skin lesions known as nodules form just under the skin’s surface. These growths are at least 1cm in size and include: 

Cysts

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Cysts are closed pockets of tissue that can be filled with fluid, air, or pus. They can develop virtually anywhere on the body and might need to be removed—particularly if cancer is suspected.

Lipomas

A raised bump underneath the skin

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Lipomas usually develop slowly beneath the skin. These noncancerous growths are made up of fatty tissue cells and might cause discomfort depending on their location. 

Pustule

A pustule is a bump no bigger than 1cm that’s filled with pus instead of clear fluid. They’re common in bacterial or fungal infections and include:

Acne Pustule

A whitehead pimple

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An example of an acne pustule is a type of pimple known as a whitehead. Whiteheads are characterized by a white tip filled with pus.

Folliculitis

A man with red bumps on his torso

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Hair follicles that become inflamed develop into pustules. This condition is known as folliculitis. The pustules from folliculitis commonly form around the genital area and on the neck.

Wheals

Wheals are raised welts that might appear red or the same color as your skin. They can be painful or itchy. They develop in response to triggers like bug bites, foods, and medications. The swellings can last for as little as an hour and rarely as long as two days.

Insect Bites

A small bump on an arm

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A raised, itchy bump sometimes appears if the body’s immune system reacts to saliva from an insect bite, like one from a mosquito. For many people, insect bites go away on their own.

Hives

Red welts

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Hives can be part of a reaction to allergens like pet dander, medicine, and pollen. Hives might also develop in response to stress, extreme cold, or excessive sweating. The welts are raised and often itchy.

Patches

A patch is described as a flat, irregularly shaped skin lesion that’s different in color than your skin tone and larger than a centimeter. Patches include:

Vitiligo

Patches of lighter skin on a person's hands

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This skin condition prompts white or lighter patches of skin to develop on the body. Experts think vitiligo is likely an autoimmune disease, where the body’s immune system mistakenly attacks skin pigmentation cells. Vitiligo isn’t curable, but there are treatments that can help make the skin tone appear more even and stop the progression.

Port-Wine Stain

A red birthmark on a child's cheek

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Abnormally dilated capillaries (tiny blood vessels) are responsible for this birthmark. Port-wine stains appear as a reddish or purplish discoloration mark that’s present at birth, commonly on the face.

Types of Secondary Skin Lesions

A secondary skin lesion is a primary skin lesion that has been changed in some way. One example would be scratching a primary lesion until a scab crusts over.

Crusts (Scabs)

Crusts are slightly elevated skin lesions that are made of dried blood or pus. They vary in size and commonly develop alongside inflammatory or infectious skin conditions. Crusts (or scabs) include: 

Impetigo Scabs

A child with yellow scabs around his mouth

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Impetigo, a bacterial skin infection common among children, causes inflamed sores on the body. Scratching these itchy, pus-filled bumps causes them to break open, which often leads to scabbing.

Scales

When the outer skin layers get dry, they tend to peel or flake—resulting in a “scaly” appearance. Scales can be triggered by factors like cold weather, hot water, or harsh products, but they’re also commonly a symptom of another condition, such as: 

Eczema Scales

A close-up of eczema

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Eczema is an inflammatory skin condition. Several types of eczema can cause scaling, including atopic dermatitis and seborrheic dermatitis. Eczema can cause a scaly, itchy, and inflamed rash on different parts of the body. A mix of genetics and environmental triggers is thought to cause eczema.

Pityriasis Rosea Scales

Scaly patches on a person's chest

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This itchy rash starts out as a round or oval-shaped skin lesion on the torso, characterized by scaling. The cause of pityriasis rosea is not fully known, though reactivation of certain human herpesviruses (HHV) that commonly infect people—HHV 6 or HHV 7—may play a role. The rash usually resolves itself within eight weeks.

Ulcers

Ulcers are circular, open wounds that develop when skin tissue is damaged by trauma, pressure, infection, or a lack of blood circulation. Specific types of ulcers include: 

Pressure Ulcers

An open, pink ulcer

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Also called bedsores, a pressure ulcer is the result of constant pressure (and sometimes friction) on the skin. This exposes the underlying skin tissue and can lead to a serious infection.

Diabetic Ulcers

A person with an open ulcer on the bottom of their foot

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People who have diabetes are prone to getting these open sores, typically on the feet. Diabetic ulcers are sometimes painless due to nerve damage in the limbs diabetes causes.

Scars

Scars naturally form when the body repairs damage from a skin injury. Scars that have just formed are usually lighter or pinkish in color and may shift closer to your natural skin color as they continue to heal.

Keloid Scars

A close-up of a man's hand and wrist, with a raised scar

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A keloid scar makes the affected skin appear raised or thickened. They vary in shape from round to elongated and may itch or cause discomfort. Keloids typically grow slowly and expand larger than the initially injured skin area.

How Are Skin Lesions Treated?

The type of skin lesion you have will dictate the type of treatment you receive. That’s why it’s important to see a healthcare provider for a thorough examination, testing, and diagnosis if you have a lesion you are concerned about.

The provider will likely start by asking for your medical history and specific symptoms before checking out the color, size, shape, and location of the lesion. Sometimes, removal is more of an aesthetic choice. Sometimes, what looks like a random rash or a harmless growth could actually be a more serious skin lesion that requires treatment or removal.

Medication

Topical medications (medicine that is applied to the skin) can help treat the lesion directly. This might include topical corticosteroids for a case of psoriasis plaques.

Oral medications are usually prescribed to promote whole-body healing. This could include a course of oral antibiotics to help treat acne.

Surgery

If a healthcare provider thinks your skin lesion looks precancerous or cancerous, they might recommend surgically removing it. Surgery might also be an option for removable lesions that are bothersome, painful, or negatively impact your quality of life. 

Surgical techniques for removing skin lesions include:

  • Shave or skin excision: Using a blade 
  • Simple scissor excision: Using curved surgical scissors 
  • Curettage and electrodesiccation: Scraping out a cancerous lesion using a device called a curette, and then burning away any remaining cells with high-frequency electrical currents 

Cryotherapy and Other Procedures

Other in-office procedures that a healthcare provider may consider include: 

  • Cryotherapy: This involves safely freezing the lesion off with liquid nitrogen. This option is effective for lesions like warts, actinic keratosis, and some cancerous skin tumors.
  • Laser therapy: This is a non-invasive procedure that uses a laser beam to target specific skin cells. Depending on the type of laser, this therapy can help with birthmarks (vascular lesions), scars, and hyperpigmentation. 

Home Care

While it’s still a good idea to check with a healthcare provider about the right treatment steps for your particular scenario, dermatologists generally recommend the following at-home care tips for common or mild skin lesions:

  • Try an oatmeal bath for itchy skin from psoriasis scales.
  • Cover blisters with a bandage to keep the area clean and prevent friction.
  • Apply calamine lotion to soothe bug bites. 
  • Keep skin clean and moisturized to avoid flaking, cracking, or bleeding.
  • Consider an over-the-counter pain reliever like acetaminophen for discomfort. 

A Quick Review

A skin lesion is an area of your skin that is different from the rest. There are many types of skin lesions. Primary lesions, such as freckles, acne, and moles, can be present at birth or form later in life. Secondary lesions, such as scars, scabs, and ulcers, develop when a primary lesion is irritated. While most lesions are not cause for concern, check with a healthcare provider if you’re worried about any skin lesion that seems to be changing, growing, or doesn’t show signs of healing. You can see if any treatment is needed or available.

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