An actinic keratosis (AK)
is a small, rough, raised area found on skin that has been in the sun for a long period of time.  Some actinic keratoses may develop into a type of skin cancer.

Causes, incidence, and risk factors
Actinic keratosis is caused by being in sunlight or exposure to ultraviolet light. You are more likely to develop this if you have fair skin, blue or green eyes, or blond or red hair; had a kidney or other transplant; take medicines that suppress the immune system; spend a lot of time each day in the sun (for example, if you work outdoors); had many, severe sunburns early in life; are older.

Symptoms
Actinic keratoses are usually found on the face, scalp, back of the hands, chest, or other sun-exposed areas.  They begin as flat and scaly areas and the the color may be gray, pink, red, or the same color as the skin. Often, it has a white or yellow crusty "scale" on top. Later it develops a hard and wart-like or gritty, rough, surface that may be easier to feel than see. 

Signs and tests
Your doctor or nurse can usually diagnose this condition by looking at your skin. A skin biopsy might be sometimes be done to see if it has progressed to a skin cancer. 

Treatment
Some actinic keratoses become squamous cell skin cancer.  That is why you should have all skin growths looked at by a doctor as soon as you find them. Your doctor will advise you how to best treat it. Growths can be removed by electrical cautery (burning), called electrodesiccation and curettage (scraping away the lesion and using electricity to kill any remaining cells), cryotherapy (freezing), or other means.  If you have many, your doctor may recommend a treatment called photodynamic therapy (PDT or "blue light"), chemical peels, or skin creams such as 5-fluorouracil (5-FU) and imiquimod.

Expectations (prognosis)
A small number of these skin growths turn into skin cancer.  Some can do this very quickly while others take quite a long time.

Prevention
You can prevent this condition by protecting your skin from sunlight or ultraviolet radiation. Wear protective clothing such as hats, long-sleeved shirts, long skirts, or pants.  Try to avoid being in the sun during midday, when ultraviolet light is most intense.  Use high-quality sunscreens, with a sun protection factor (SPF) rating of at   least 15 and that blocks both UVA and UVB light.  Apply sunscreen before going out into the sun, and then reapply often.  It is necessary to use sunscreen year-round, including in the winter.  Also avoid sun lamps, tanning beds, and tanning salons.

Other important sun safety facts:
  • Sun exposure is stronger in or near surfaces that reflect light, such as water, sand, concrete, and areas painted white.
  • Sun exposure is more intense at the beginning of the summer.
  • Skin burns faster at higher altitudes.
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