Seborrheic keratosis

Seborrheic keratosis are benign lesions that don't necessarily look benign. They can have various colors, grow quickly, itch, & sometimes bleed. They are fairly easy to distinguish from skin cancers.

Seborrheic Keratosis / Barnacles on the Skin

Skin lesions that don't ever turn into cancer, seborrheic keratoses, or Seb K's for short, can look dangerous. In reality they are just annoying. Also irreverently called barnacles, they come in all different shapes and sizes from large black growths to barely noticeable raised areas.

Characteristics of Seborrheic Keratosis

The wicked witch with a wart on her nose probably had a Seb K not a wart. So how can you tell if that bump on your face or chest is actually a Seb K? They do have some defining characteristics.

1. Stuck on - They are classically described as looking like someone took clay or a blob of dirt and "stuck" it on the skin. The edge of the seborrheic keratosis is not attached to the underlying skin making it appear that it could be removed by picking it off with your fingernail. This is because seborrheic keratoses arise from the epidermis, or top layer of skin. They don't extend deep into the skin like warts. What you see is what you get.

2. Warty surface - Seborrheic keratoses may look like warts but they don't contain human papilloma viruses that cause warts. As they develop some can have a very rough surface with deep pits and fissures almost like cauliflower being pulled apart.

3. Smooth surface with horn pearls - Some seborrheic keratoses don't have a rough surface. If they are smooth, they contain tiny bumps that look like seeds that are lighter or darker than the surrounding tissue. These are called horn pearls and they are actually bits of keratin that develop in a whirling, circular pattern. Sometimes these horn pearls are best seen with a magnifying glass.

4. Itching - For some reason seborrheic keratoses tend to itch especially the older we get. Some people will unintentionally manipulate or "pick at" a seborrheic keratosis and cause it to be further irritated. If irritated enough, the skin around it can become red and the seborrheic keratosis itself can bleed. This can be alarming to savvy skin-watchers who know that a doctor should see any lesion that bleeds.

What can be done about Seborrheic Keratosis?

The first and usually the best choice is to leave them alone. They may get larger, but they are not precancerous so leaving them there for the life of your skin is not a problem. Seborrheic keratoses are usually removed because they itch, they interfere with clothing or jewelry, or they are cosmetically unacceptable. That last option is a judgment call. The warty thing on an 80-year-old man's nose may not be as big of a deal as the one on a 40-year-old woman's nose.

Removing Seborrheic Keratosis

If you decide to have a seborrheic keratosis removed, there are several ways to do this.

1. Liquid Nitrogen - A small seborrheic keratosis can be frozen with liquid nitrogen. Liquid nitrogen works by freezing and destroying the cells but leaving the connective tissue foundation intact. The lesion frozen forms a blister as the water is released from the now-dead cells then crusts over as that water dries. When the crust falls off after several days, the skin underneath has begun to repair itself. Liquid nitrogen can leave a scar as the repaired skin may have more or less pigment producing cells. The scar is usually flat though unless you have a tendency to form keloids.

2. Shave - Another way seborrheic keratoses can be removed is to shave them off. Because their attachment to the underlying skin covers less area than the lesion itself, shaving can be a viable option. Seborrheic Keratoses are shaved off with a flexible razor blade going just deep enough to get only the seborrheic keratosis cells and leave normal skin. Shaving too much normal skin off can leave a divot in the skin as a scar. After the lesion is shaved, a chemical agent such as aluminum chloride or silver nitrate is applied to the wound to stop any small surface bleeding. Silver nitrate is a dark brown color and the resulting wound after the shave is dark brown. This color will usually go away after the skin repairs but some of that pigment can remain. For this reason, silver nitrate is usually not used on the face.

Unusual-Looking Growths

Sometimes seborrheic keratoses can be very difficult to distinguish from melanoma. Especially when they first appear, they can have several of the characteristics of atypical growths. They can have an irregular border and color variation throughout the lesion. You should not hesitate to see your doctor about any skin rashes or bumps that concern you.

Seborrheic keratoses (SKs) are common skin growths. These benign (non-cancerous) growths can occur almost anywhere on the skin. Some people get just one; 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. A 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. A 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.


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.


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.


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.


Since SKs are benign, treatment is generally not necessary. There are times, though, when these lesions should be examined by a dermatologist. Sometimes a SK grows quickly, 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 dermatologist. This can indicate a serious health problem.

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


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 dermatologist 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 dermatologist. These are signs of skin cancer, and early detection of skin cancer is the best way to ensure successful treatment.

What Are They?

Seborrheic keratoses are benign (noncancerous) skin growths that develop from skin cells called keratinocytes. These growths have a waxy or greasy look and can be tan, brown or black. They look like they have been glued or stuck onto the skin. Over time, the growths become rough and crusty looking.

Seborrheic keratoses usually appear alone, but others may develop. They usually are found on the chest and back but can appear anywhere on the body, including the face, scalp and neck.

No one knows what causes seborrheic keratoses, but they become more common with age. Most people will develop some seborrheic keratoses as they get older, and children rarely have them. Seborrheic keratoses are not contagious.


Seborrheic keratoses look like crusty growths on the skin that typically start out tan or brown but can darken over time. They tend to have a greasy appearance and look as though they were glued onto the skin, as opposed to growing from it. They may be tiny, or larger than 3 inches across. They rarely itch.



Physicians usually can diagnose seborrheic keratoses by looking at them. In rare cases, seborrheic keratoses may look like other skin disorders, including malignant melanoma. If the diagnosis is uncertain, your physician may want to do a biopsy, in which a portion of the growth is removed and examined under a microscope.


Expected Duration

Seborrheic keratoses do not go away on their own. If they are not removed, they will last a lifetime.



There is no way to prevent seborrheic keratoses from developing.


Seborrheic keratoses do not require treatment. Although they may grow relatively large and can become dark, they are not dangerous. If seborrheic keratoses become irritated, itchy or unsightly or if they bleed, they can be removed in a doctor's office. Because the skin is numbed before any procedure, treatment is mostly painless. The three main methods of removal are:

  • Curettage After the skin is numbed, the growths are sliced or scraped off using an instrument called a curette.
  • Cryosurgery or freezing Liquid nitrogen is applied to the growths. The seborrheic keratoses crust over and then fall off a few weeks later.
  • Electrosurgery An electric current burns the growths off.

When To Call A Professional

See a health care professional if you develop any unusual skin growths or if existing growths start to change their appearance. If multiple seborrheic keratoses develop suddenly, call your physician's office to schedule an appointment. It may be a sign of another disease.


Seborrheic keratoses do not go away on their own, but they can be removed if they become irritating or unsightly. There is no harm in not treating the growths, because they are benign (noncancerous) and do not become cancerous.