What is seborrheic keratosis?
Seborrheic keratosis (seb-o-REE-ik care-uh-TOE-sis) 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.
Seborrheic keratoses range in color from white to black; however, most are tan or brown.
You can find these harmless growths anywhere on the skin, except the palms and soles. Most often, you’ll see them on the chest, back, head, or neck.
A seborrheic keratosis usually looks like a waxy or wart-like growth. It typically appears on the face, chest, shoulders or back of the body. You may develop a single growth or cluster of them. A seborrheic keratosis:
- Varies in color, usually from light tan to brown or black
- Is round or oval shaped
- Has a characteristic “pasted on” look
- Is flat or slightly elevated with a scaly surface
- Ranges in size from very small to more than 1 inch (2.5 centimeters) across
- May itch
Multiple lesions may appear, although at the beginning there may be just one. Growths can be found on many areas of the body, including the:
Growths can be found anywhere on the body except on the soles of the feet or the palms.
Growths often start out as small, rough areas. Over time, they tend to develop a thick, wart-like surface. They’re often described as having a “stuck-on” appearance. They may also look waxy and have slightly raised surfaces.
Growths are usually round or oval-shaped.
Growths are usually brown, but they can also be yellow, white, or black.
When to see a doctor
Seborrheic keratoses aren’t usually painful, but they can be bothersome depending on their size and location. Be careful not to rub, scratch or pick at them. This can lead to bleeding, swelling and, in rare cases, infection.
A seborrheic keratosis isn’t dangerous, but you shouldn’t ignore growths on your skin. It can be difficult to distinguish between harmless and dangerous growths. Something that looks like seborrheic keratosis could actually be melanoma.
Have a healthcare provider check your skin if:
- there’s a new growth
- there’s a change in appearance of an existing growth
- there’s only one growth (seborrheic keratosis usually exists as several)
- a growth has an unusual color, such as purple, blue, or reddish-black
- a growth has borders that are irregular (blurred or jagged)
- a growth is irritated or painful
If you’re worried about any growth, make an appointment with your doctor. It’s better to be too cautious than ignore a potentially serious problem.
The exact cause of seborrheic keratoses isn’t known. They are very common and generally increase in number with age. The lesions aren’t contagious. They tend to run in some families, so inheritance may play a role.
You can develop seborrheic keratoses at any age, but you’re generally more likely to develop them if you’re over age 50. You’re also more likely to have them if you have a family history of the condition.
Who is at risk of developing seborrheic keratosis?
Frequent sun exposure
There is some evidence that skin exposed to the sun is more likely to develop a seborrheic keratosis. However, growths also appear on skin that is usually covered up when people go outdoors.
Family members with seborrheic keratosis
This skin condition often runs in families. Risk increases with the number of affected relatives.
Diagnosing seborrheic keratosis
A dermatologist will often be able to diagnose seborrheic keratosis by eye. If there’s any uncertainty, they’ll likely remove part or all of the growth for testing in a laboratory. This is called a skin biopsy.
The biopsy will be examined under a microscope by a trained pathologist. This can help your doctor diagnose the growth as either seborrheic keratosis or cancer (such as malignant melanoma).
Common treatment methods for seborrheic keratosis
In many cases, a seborrheic keratosis doesn’t need treatment. However, your doctor may decide to remove any growths that have a suspicious appearance or cause physical or emotional discomfort.
Methods of removal
Three commonly used removal methods are:
- Cryosurgery, which uses liquid nitrogen to freeze off the growth.
- Electrosurgery, which uses an electrical current to scrape off the growth. The area is numbed before the procedure.
- Curettage, which uses a scoop-like surgical instrument to scrape off the growth. It’s sometimes used with electrosurgery.
Your skin may be lighter at the site of removal. The difference in skin color often becomes less noticeable over time. Most of the time a seborrheic keratosis won’t return, but it’s possible to develop a new one on another part of your body.