Actinic Keratoses (AK)

Dermatology A to Z


What causes actinic keratoses?

Repeated, prolonged sun exposure causes skin damage, especially in fair-skinned individuals. Sun-damaged skin becomes dry and wrinkled and may form rough, scaly spots called actinic keratoses (AK). These rough spots remain on the skin even though the crust or scale is picked off. Treatment of an actinic keratosis requires destruction of the defective skin cells. New skin then forms from the deeper skin cells, which have escaped sun damage. Why treat actinic keratoses? Some physicians believe actinic keratoses are not skin cancers, rather a pre-cancerous condition. Others, however, feel they are actually an early form of a skin cancer called squamous cell carcinoma. Because they may sometimes become cancerous, however, they should be removed.


Typically, actinic keratoses are treated by freezing them with liquid nitrogen. Freezing causes blistering and shedding of the sun-damaged skin. Occasionally, they are scraped from the skin with an instrument called a curette. Sometimes we are not sure if the growth is harmless. When this occurs, I prefer to cut the growth off and send it for microscopic analysis (biopsy). Healing after removal usually takes two to four weeks, depending on the size and location of the keratosis. Hands and legs heal more slowly than the face. The skin’s final appearance is usually excellent. If the lesion recurs or does not respond to liquid nitrogen, another office visit and/or treatment may be required.

When there are many keratoses, a useful treatment is the application of 5-fluorouracil (5-FU). The medication is rubbed on the keratoses for 10 to 20 days; 5-FU destroys only sun-damaged skin cells. After three to five days, the treated area starts to get raw and angry-looking. The applications are continued until your physician determines that you have the needed results. Healing starts when the 5-FU is stopped. Aldara® and Solaraze are other topical treatments that provide similar results.

Photodynamic therapy (PDT) is a new approach to treating large areas that have many AKs. Levulan is applied to the skin. After a short time, a special blue light activates the medication.  This active form of the medication destroys the bad skin cells.

Depending on the number and size of the actinic keratoses, extent of actinic skin damage and history of skin cancer, you will be asked to return to the clinic every 6 months to 1 year. This is truly a case of prevention being easier than treatment of skin cancer. Untreated actinic keratosis are likely to progress to skin cancer (10-20% over 10 yrs.) They are not medical emergencies but do merit treatment and attention.


Sun damage is permanent. Once sun damage has progressed to the point where actinic keratoses develop, new keratoses may appear even without further sun exposure. You should avoid excessive sun exposure- but don’t go overboard and deprive yourself of the pleasure of being outdoors. Reasonable sun protection should be your aim. In general, always use a sunscreen (sunscreens are not the same as tanning lotions or oils). Sunscreens are measured by SPF (sun protection factor). Try to get a screen with a SPF of 15 or higher. I recommend at least a SPF of 30. Some sunscreens resist being washed away by sweat or even by swimming; however, even all day sunscreens need to be reapplied every few hours. Remember: anytime you are outdoors, even in the shade, you are being exposed to UV (ultraviolet) radiation and should use a sunscreen — even in the winter. Sun protective clothing is also available. Visit Solumbra for more information on Sun Protection.