Seborrheic Keratosis (SK)

Seborrheic keratoses (SKs) are common, non-cancerous lesions that grow on the outer layer of the skin (epidermis). Though they may appear to spread, SKs are not contagious.


SKs can develop on any part of the body.

  • Usually begins as rough, itchy bumps
  • Can thicken and darken to brown or black over time
  • Usually round- or oval-shaped with an elevated, rough surface
  • Sometimes seems to be glued to the skin or dropped on like candle wax
Although harmless, SKs can sometimes resemble other skin disorders, such as warts, actinic keratosis, moles, and melanomas. So they should be observed regularly for any changes in size, shape, or color. Any growth that bleeds, itches, or becomes irritated should be checked by a physician.

SK or something else?

  • Warts are caused by a virus. They are usually not as dark and do not appear to have been pasted on as SKs do.
  • Actinic keratoses (AKs) represent a very early stage of skin cancer and develop on sun-exposed parts of the body. AKs are usually flatter, redder, and rougher than SKs.
  • Moles (also known as nevi) can be similar in color but are more commonly developed during childhood. Most people develop 20-30 moles during their lifetime.
  • Melanomas can sometimes be confused with SKs because they can both be dark in color and have irregular shapes.

Learn how to examine your skin

Risk factors of seborrheic keratosis

There is no known cause of SKs to date. However, the lesions do become more common with age and may develop during pregnancy or estrogen treatments.

Potential consequences

SKs are not a sign of serious health issues except in very rare instances when they develop suddenly in very large numbers and can be associated with internal malignancies.
SKs often develop in those who are middle-aged, and likelihood increases with age.
Source: Healthline

Treatment options for seborrheic keratosis

SKs do not go away on their own, but can be removed if they become irritating or unsightly.

  • Cutting off the lesion with a small, flat blade under local anesthesia (shave removal)
  • Freezing lesions with liquid nitrogen (cryosurgery)
  • Scraping the lesion from the skin (curettage)
  • Burning the lesion off with electric current (electrosurgery)

Preventing seborrheic keratosis

To protect yourself from seborrheic keratosis, the most important prevention measure you can take is to avoid overexposure to sunlight.

You should also inspect your entire body regularly for any skin changes, and routinely visit your physician for a skin examination.

Learn more about recommended prevention and protection techniques from Spot the Spot.

Get protection tips

Seborrheic keratosis resources


Review information on seborrheic keratosis or other skin disorders with your dermatologist. Download or print these brochures and bring them to your next appointment.

Open SK brochure Open skin disorders brochure
SKs do not go away on their own, but can be removed if they become irritating or unsightly.
Source: Harvard Health

Other types of skin cancer

  • Also known as solar keratosis, AK is a precancerous lesion of the outer layer of skin.
  • Also known as atypical moles, these benign lesions look different than common moles.
  • This is the most common form of skin cancer and usually occurs on sun-exposed areas of the body.
  • This serious form of skin cancer affects the cells that produce melanin.
  • This major cancer arises from the outer layer of the skin and mucous membranes.