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Seborrheic Keratosis: Treatment and Causes

What Causes Seborrheic Keratosis?
Who Is at Risk?
Where Do They Appear?
When Is Treatment Needed?
Seborrheic Keratosis Treatment Options
What Seborrheic Keratosis Are Not

Seborrheic keratoses (SKs) are common skin growths. These benign (non-cancerous) growths can occur almost anywhere on the skin. Some people get just one while others develop many. Having many SKs is more common.

Usually beginning as small, rough bumps, SKs tend to eventually thicken and develop a warty surface. Most are brown, but these growths range in color from light tan to black. Some SKs measure a fraction of an inch; others are larger than a half-dollar. An SK can be flat or raised. Sometimes the surface feels smooth.

What often distinguishes these growths from other lesions is a waxy, pasted-on-the-skin appearance. An SK can look like a dab of warm, brown candle wax on the skin. It also may resemble a barnacle attached to a ship. Either way, SKs tend to have that stuck-on-the-skin appearance.

What Causes Seborrheic Keratosis?

While the exact cause remains unknown, researchers have discovered some key findings. SKs seem to run in families, and it appears that some people inherit a tendency to develop many SKs.

Although these growths develop on both sun-exposed and non-sun-exposed skin, some studies suggest that sun exposure may play a role. The exact cause is unknown. And while SKs may seem to multiply and spread to other areas, they are not contagious.

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Who Is at Risk?

While anyone may develop SKs, these growths generally first appear in middle age or later. Occasionally, SKs erupt during pregnancy or following estrogen therapy. Children rarely have SKs.

Where Do They Appear?

Most often forming on the chest and back, SKs also can be found on the scalp, face, neck, or almost anywhere on the skin. They do not develop on the palms or soles.

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When Is Treatment Needed?

Since SKs are benign, treatment is generally not necessary. There are times, though, when these lesions should be examined by a Water’s Edge Dermatology practitioner.

Sometimes an SK grows quickly and turns black, itches, or bleeds, making it difficult to distinguish from skin cancer. Such a growth must be biopsied (removed and studied under a microscope) to determine if it is cancerous or not.

Occasionally, numerous new SKs develop suddenly. If this occurs, see a Water’s Edge Dermatology practitioner. This can indicate a serious health problem.

Treatment may be recommended if the growth is large or easily irritated by clothing or jewelry. Sometimes, an SK is treated because the patient considers it unsightly. In these last two cases, there are a few treatment options.

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Seborrheic Keratosis Treatment Options

Cryosurgery, electrosurgery, and curettage are the most common options for removing SKs.


Liquid nitrogen, a very cold liquid, is applied to the growth with a cotton swab or spray gun. This “freezes” the growth. The SK usually falls off within days. Sometimes a blister forms under the SK and dries into a scab-like crust that falls off.

After the growth falls off, a small dark or light spot may appear on the skin. This usually fades over time. A permanent white spot is a possible side effect of this treatment.

Electrosurgery and Curettage

Electrosurgery involves anesthetizing (numbing) the growth and using an electric current to cauterize (burn) the growth. A scoop-shaped surgical instrument called a curette is used to scrape off the treated lesion. This is the curettage.

Stitches are not necessary. There may be minimal bleeding, which is controlled by applying pressure or a blood-clotting chemical. Sometimes only electrosurgery or curettage is necessary.

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What Seborrheic Keratosis Are Not

SKs can resemble warts, moles, actinic keratoses (growths caused by years of sun exposure that are considered the earliest possible stage in the development of skin cancer), and skin cancer. While SKs can resemble these lesions, there are differences that help dermatologists distinguish seborrheic keratoses from other lesions.

Warts tend to develop more quickly than SKs and cluster in small areas. Warts also do not get as dark, and they do not have that pasted-on-the-skin appearance.

Moles normally appear during childhood and adolescence. By the age of 30, a person usually has all the moles that will develop. SKs generally do not appear until middle age or later. SKs also tend to have that pasted-on-the-skin look, which moles do not have.

Actinic keratoses (AKs) are flatter and rougher than SKs. Since years of sun exposure cause AKs, these lesions form on skin that has received lots of sun such as the face, neck, hands, and forearms. A Water’s Edge Dermatology practitioner should examine all growths and patches of skin that feel dry, scaly, and rough-textured.

Melanoma, a type of skin cancer that can be lethal, may look just like a SK. Both can become very dark and irregular in shape.

If the growth darkens, bleeds, itches, or is irritated, it should be examined by a Water’s Edge Dermatology practitioner. These are signs of skin cancer, and early detection is the best way to ensure successful skin cancer treatment.

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