Keratosis is the general term for a skin disorder that causes an overgrowth of keratin – a protein that makes up skin, hair, and nails – on the skin or mucous membranes. There are three primary types of keratosis: seborrheic keratosis, actinic keratosis, and keratosis pilaris. Symptoms and treatment vary according to the type of disorder, but all forms of keratosis involve growths on the skin. Seborrheic keratosis and keratosis pilaris are harmless, but actinic keratosis can develop into skin cancer if it is not identified early and treated.

Symptoms and Diagnosis

Symptoms and severity vary according to the type of keratosis. A seborrheic keratosis is a common noncancerous (benign) skin growth with a wart-like texture that is commonly diagnosed in older adults. These growths can be brown, black, or pale and are most often found alone or in groups on the head, neck, or trunk of the body. Seborrheic keratoses do not cause skin cancer or require treatment. An actinic keratosis is a small, rough, scaly patch of skin in an area that has been exposed to sunlight for years. An actinic keratosis takes years to develop and is usually precancerous, which means that it can develop into skin cancer. It is usually found on the face, lips, ears, hands, forearms, scalp, or neck. Actinic keratoses may itch or burn and range in color from red or brown to flesh-colored. When left untreated, some actinic keratoses develop into squamous cell carcinoma, a serious form of skin cancer. Keratosis pilaris causes small, acne-like bumps on the arms, thighs, cheeks, and buttocks. These bumps are white or red, may be itchy, and worsen when skin is dry. All forms of keratosis can be diagnosed by visual inspection, but skin biopsies may be done to rule out skin cancer.


The cause of seborrheic keratosis is not known, but growths are thought to be genetic and increase with age. Actinic keratosis is caused by long-term or intense exposure to UV rays, either from the sun or tanning lamps and beds. People with pale skin and light hair and eyes are more likely to develop actinic keratosis. Keratosis pilaris bumps occur when hair follicles are plugged by keratin, a protein that makes up the skin, hair, and nails. It is not known why keratin builds up in hair follicles, but it often occurs with other skin conditions and genetic diseases, although it is also common in healthy people. Continue reading for Prevention and Treatment Information . . .

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