Actinic keratosis is a small, rough, raised area found on skin that has been exposed to the sun over a long period of time.

Over many years, some actinic keratoses may develop into a type of skin cancer.

Solar keratosis; Sun-induced skin changes - keratosis; Keratosis - actinic (solar)

Actinic keratosis is caused by sun exposure, but it takes many years or decades to develop.

Risk factors for actinic keratosis include:

• Having fair skin, blue or green eyes, or blond or red hair
• History of kidney or other solid organ transplant (people who take medicines that suppress the immune system)
• Long-term, daily sun exposure (for example, if you work outdoors)
• Multiple, severe sunburns early in life
• Older age

Actinic keratosis is usually found on the face, scalp, back of the hands, chest, or other sun-exposed areas.

They may be gray, pink, red, or the same color as the skin. Often, they have a white or yellow scale on top.

• They begin as flat and scaly areas
• Later they develop a hard and wart-like or gritty, rough, and "sandpapery" surface -- may develop a horn-like texture

The skin lesion may be easier to feel than to see.

The health care provider makes the diagnosis based on the appearance of the skin growth. A skin biopsy may be done for larger and thicker actinic keratoses to make sure no cancer is present.

Because about 5% of actinic keratoses go on to develop into squamous cell skin cancer, have them examined promptly. Follow your health care provider's advice for treatment.

Growths may be removed by:

• Burning (electrical cautery)
• Scraping away the lesion and using electricity to kill any remaining cells (caled curettage and electrodesiccation)
• Cutting the tumor out and using stitches to place the skin back together (called excision)
• Freezing (cryotherapy, which freezes and kills the cells)

When many actinic keratoses are found, treatments that cause irritation and redness over a larger area are used:

• A laser treatment called photodynamic therapy
• Chemical peels
• Creams such as 5-fluorouracil (5-FU) and imiquimod

Actinic keratosis itself is harmless ( benign), but about 5% develop into skin cancer.

Removal of the growth is usually effective.

• Irritation and discomfort of the skin growth
• Scarring from the treatment
• Squamous cell carcinoma

Call for an appointment with your health care provider if areas of persistent roughness or scaliness develop in sun-exposed skin.

Reduce sun exposure and protect your skin from the sun:

• Wear protective clothing such as hats, long-sleeved shirts, long skirts, or pants.
• Try to avoid sun exposure during midday, when ultraviolet light is most intense.
• Use high-quality sunscreens, preferably with a sun protection factor (SPF) rating of at least 15. Pick a sunscreen that blocks both UVA and UVB light.
• Apply sunscreen before going out into the sun, and reapply often.
• Use sunscreen year-round, including in the winter.
• Avoid sun lamps, tanning beds, and tanning salons.

Other important sun safety facts to keep in mind:

• 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.

Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier;2009:pp 812-818.

Ibrahim SF, Brown MD. Actinic keratoses. In: Lebwohl M, ed. Treatment of Skin Disease: Comprehensive Therapeutic Strategies. 3rd ed. Philadelphia, Pa: Saunders Elsevier; 2009.