Actinic Keratosis Basics

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What Is Actinic Keratosis?

Actinic keratoses are lesions on the outer skin layer caused by too much exposure to the ultraviolet rays of sunlight. They are also the early beginnings of skin cancer, most often appearing after age 40. In some areas where climate is mild year-round -- like Florida and California -- these lesions appear in much younger people, even teenagers.

People with fair skin, blond or red hair, blue or green eyes are most at risk of developing these rough, scaly-skinned "bumps." A history of burning rather than tanning also increases risk. If not treated, these bumps can develop into a more serious form of skin cancer.

To prevent actinic keratoses, it's important to:

• avoid exposure to sunlight during peak sunlight hours (10 a.m. to 4 p.m.)
• wear clothing that covers arms and legs
• wear a wide-brimmed hat or carry an umbrella during peak sunlight hours
• use sunscreen with sun protection factor (SPF) of 15 or higher, applying it at least 15 to 30 minutes before sun exposure, even in the winter
• choose a sunscreen that provides both UVA and UVB protection
• reapply sunscreen every two hours when outdoors, even on cloudy days.

Medically reviewed by Tracy Shuman, MD, July 2005.

SOURCES: American Academy of Dermatology. Department of Clinical Social Medicine, University of Heidelberg, Germany.

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