Understanding Actinic Keratosis -- the Basics

Medically Reviewed by Debra Jaliman, MD on May 17, 2021

What Is Actinic Keratosis?

Actinic keratoses (plural of actinic keratosis) describes lesions on the outer skin layer caused by too much exposure to the ultraviolet rays of sunlight. They are also the 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.

People with fair skin, blond or red hair, and blue or green eyes are most at risk of developing these rough, scaly patches, or keratoses. A history of a sunburn also increases the risk. If not treated, these patches can develop into a more serious form of skin cancer, although this is unusual.

To prevent actinic keratosis, it's important to:

  • Avoid exposure to sunlight during peak sunlight hours (10 a.m. to 2 p.m.).
  • Wear clothing that covers arms and legs.
  • Wear a hat with a brim of at least 2 inches wide that protects the ears -- not just a cap -- or carry an umbrella when outdoors during peak sunlight hours.
  • Use sunscreen with sun protection factor (SPF) of 30 or higher, applying it at least 15 to 30 minutes before sun exposure.
  • Choose a sunscreen labeled “broad-spectrum” or states that it provides both UVA and UVB protection.
  • Reapply sunscreen every two hours when outdoors, even on cloudy days.
  • Reapply sunscreen more frequently than every two hours if you are sweating, and reapply it immediately after getting out of the water. Use a sunscreen that is water-resistant for 40 minutes or longer.
  • Remember that it is the light from the sun that can be dangerous -- not the heat -- so you can be at risk even if the temperature is mild.


Show Sources

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

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