Seborrheic Keratoses

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Your doctor has determined that you have one or more seborrheic keratoses, which are the most common benign, or harmless, skin growths that affect people over the age of 30. They are not cancer and do not increase the risk of developing skin cancer. Almost all adults develop one or a few seborrheic keratoses (SKs) and some may have many, often in clusters. The condition is more likely with advancing age, and the number of growths often increases over the years.

About the Condition

The skin is the largest organ of the body. Its top layer is the epidermis, which provides protection against the environment. The second layer of the skin is the dermis, which supplies blood, oxygen, strength and support. Underneath the dermis is the hypodermis, or subcutaneous fat layer, which provides an ongoing blood supply to the dermis.

Seborrheic keratoses occur when raised, non-contagious growths form on the outer layer of skin. The exact cause is not known, but the tendency to develop SKs seems to be inherited. Sun exposure does not appear to be a factor in their development.

The distinguishing feature of seborrheic keratoses is a waxy, pasted-on look reminiscent of warm candle wax stuck to the skin. They are usually brown in color, but can range from white or light tan to black. Their diameter may vary from a fraction of an inch to larger than an inch, and they can grow larger over time. Sometimes small white or black circles, called horn cysts, may appear within the growth itself.

When they first arise, seborrheic keratoses usually look like small light brown bumps. As they grow slowly over time, they darken and thicken, forming an uneven, rough, warty surface. SKs typically develop on the chest or back, although they can appear on many other parts of the body including the scalp, face, neck and legs. They often arise during pregnancy, after hormone replacement therapy or in conjunction with other medical conditions.

SKs can be confused with other growths such as warts, moles and melanoma skin cancer. Those conditions, however, do not have a pasted-on appearance and differ in the following ways:

•  Warts are caused by a virus, usually develop more quickly and are not as dark
•  Moles are affected by sun exposure, usually fade or disappear over many years and may occasionally develop into skin cancer
•  Melanomas are caused by long-term sun damage and are usually dark brown to bluish-black

Since very dark seborrheic keratoses can be mistaken for or blend in with melanoma skin cancer, it is a good idea to have them thoroughly checked by a doctor.

Treatment Options

Seborrheic keratoses can be left untreated if they are not causing any problems. In cases where they get in the way of shaving, are cosmetically undesirable, itch or bleed excessively or become irritated by clothing or other sources of contact, they can be removed by a doctor. One of several methods may be used, depending on the size and location of the growth. Sometimes more than one treatment may be used at the same time. The following treatment possibilities are available:

Cryosurgery The preferred removal method for SKs is cryosurgery, which uses super-cooled gas to freeze and destroy lesions.

Excision Cutting off seborrheic keratoses with a scalpel (excision) is another treatment that is sometimes used.

Curettage This procedure uses a curette (sharp scooping instrument) to scrape of SKs.

Electrocautery In electrocautery, an electrified needed is used to destroy seborrheic keratoses.

Laser Therapy Sometimes a high-intensity light, or laser, is used to burn off SKs.

Dermabrasion SKs can also be removed by "sanding" them off, known as dermabrasion.

What You Can Do

There is nothing that can be done to prevent the development of seborrheic keratoses, and occasionally they may come back after being removed. If they do return, or if you develop any other changes in your skin, be sure to promptly report them to your doctor. Also, be sure not to scratch or pick at your seborrheic keratoses because the crumbly scale that comes off will recur, and you could cause a skin infection to develop.

To maximize your health and minimize your risk of ever developing skin cancer, you should strive to prevent skin damage from ultraviolet (UV) ray exposure. General steps you can take include:

•  Avoiding the sun, especially between 10 a.m. and 4 p.m. when UV rays are the strongest
•  Using SPF 15 or higher sunscreen that contains avobenzone (Parsol 1789), titanium dioxide and/or zinc oxide, applying it 20 minutes before going outdoors and again every two hours, or immediately after swimming or sweating
•  Wearing a wide-brimmed hat and 100% UV-blocking sunglasses when outdoors
•  Avoiding tanning salons and other UV tanning devices
•  Visiting your doctor regularly for skin checks and promptly reporting any changes in your skin

Additional Resources

American Academy of Dermatology, 888.462.3376,

This patient resource sheet is provided to you as a service of CBLPath® and is intended for information purposes only. It may not fully describe all aspects of your diagnosis and is not meant to serve as medical advice or a substitute for professional medical care. Your physician can provide you with a thorough explanation of your diagnosis and appropriate treatment options, which may vary. Only you and your physician can determine your best treatment plan.

Updated 9.07