There are two kinds of keratoses, actinic and seborrheic. Only one of them is associated with a greater skin cancer risk. Actinic keratoses
These are scaly papules which occur on exposed skin of older, fairer-skinned, persons resulting from chronic overexposure to ultraviolet light from the sun. Actinic or "Solar" keratoses are mostly found on sites repeatedly exposed to the sun especially the backs of the hands and the face, most often affecting the nose, cheeks, upper lip, temples and forehead. They are especially common in fair-skinned persons or those who have worked outdoors for long periods. A small percentage of these lesions do develop into invasive squamous cell carcinoma.###

Prevention of actinic keratoses should ideally begin early in life. In geographic areas of high-intensity sunlight, sun damage to unprotected skin begins in childhood and puts the child at high risk for actinic keratoses and skin cancer later in life. However, it is never too late to initiate prevention of new actinic keratoses lesions in adulthood. Use a sunscreen with sun protection factor (SPF) of 15 or higher, applying it at least 15-30 minutes prior to sun exposure for maximum sun protection. Select a broad-spectrum sunscreen that provides both UVA and UVB protection. Sunscreen should be reapplied as necessary.

Seborrheic Keratoses
Although Seborrheic Keratoses (seb-o-REE-ick Ker-ah-TOE-sees) are often confused with moles, warts, and melanoma skin cancer, they differ in a variety of ways. Seborrheic keratoses are non-cancerous growths of the outer layer of skin. There may be just one growth, or many which occur in clusters. They are usually brown, but can vary in color from light tan to black. They vary in size from a fraction of an inch in diameter to larger than a half-dollar. A main feature of seborrheic keratoses is their waxy, "pasted-on" or "stuck-on" look. They sometimes look like a dab of warm brown candle wax that has dropped onto the skin.

Although the exact cause of seborrheic keratoses is not known, almost everybody will eventually develop at least a few of these growths. They are sometimes referred to as the "barnacles of old age". These become more common and more numerous with advancing age.

Some people develop many over time, while others develop only a few. Sometimes seborrheic keratoses may erupt during pregnancy, following estrogen therapy, or in association with other medical problems.

Seborrheic keratoses are most often found on the chest or back, although, they can also be found on the scalp, face, neck, or almost anywhere on the body. They appear less often below the waist. Since they are not caused by sunlight, they can be found on sun-exposed or covered areas. When they first appear, the growths usually begin one at a time as small, rough, itchy bumps. Eventually, they thicken and develop a rough, warty surface.

Children rarely develop seborrheic keratoses. Although seborrheic keratoses may first appear in one spot and seem to spread to another, they are not contagious. As people age they may simply develop a few more.

They can get irritated by clothing rubbing against them. Because they may grow larger over the years, removal is sometimes recommended especially if they itch, get irritated, or bleed easily. A seborrheic keratosis may turn black and may be difficult to distinguish from skin cancer. Sometimes such a growth must be removed and studied under a microscope to determine if it is cancerous or not.

Treatment
Both kinds of keratoses can be treated by some similar methods. One method is called cryosurgery, or freezing. A very cold liquid called liquid nitrogen is applied to the growth with a cotton swab, or spray gun, to freeze it. The keratosis usually falls off within a few weeks. No mark is usually left when it heals, although occasionally there may be a small spot that will usually fade over time.

Another method is called curettage. The growths are removed by scraping them from the surface of the skin. An injection or spray is first used to numb the area before the growth is removed. No stitches are necessary, and bleeding is limited. Electrosurgery is another form of treatment. The growth is first numbed, then burned using an electric current, and scraped off.

Actinic keratoses are usually treated more aggressively than seborrheic keratoses because they can develop into skin cancer. Actinic keratoses can also be treated by retinoids (vitamin A derivatives), topical chemotherapy (5-fluoruracil), chemical peel, dermabrasion and laser skin resurfacing.