CausesBy Mayo Clinic staff
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|Basic skin layers|
Frequent or intense exposure to UV rays, typically from the sun, causes an actinic keratosis.
An actinic keratosis begins in your skin's top layer — the epidermis. The epidermis is as thin as a pencil line, and it provides a protective layer of skin cells that your body continually sheds.
Normally, skin cells within the epidermis develop in a controlled and orderly way. In general, healthy new cells push older cells toward the skin's surface, where they die and eventually are sloughed off. When skin cells are damaged through UV radiation, changes occur in the skin's texture and color, causing blotchiness and bumps or lesions.
Most of the damage to skin cells results from exposure to UV radiation from sunlight and commercial tanning lamps and beds. The damage adds up over time, so the more time you spend in the sun or in a tanning booth, the greater your chance of developing skin cancer. Your risk increases even more if most of your outdoor exposure occurs at times of the day or in locations where the sunlight is most intense.
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