Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Sun-Damaged Skin (Actinic keratosis)

What Is It?

Although most people love the warmth and light of the sun, too much sun exposure can significantly damage human skin. The sun's heat dries out areas of unprotected skin and depletes the skin's supply of natural lubricating oils. In addition, the sun's ultraviolet (UV) radiation can cause burning and long-term changes in the skin's structure.

The most common types of sun damage to the skin are:

• Dry skin — Sun-exposed skin can gradually lose moisture and essential oils, making it appear dry, flaky and prematurely wrinkled, even in younger people.

• Sunburn — Sunburn is the common name for the skin injury that appears immediately after the skin is exposed to UV radiation. Mild sunburn causes only painful reddening of the skin, but more severe cases can produce tiny fluid-filled bumps (vesicles) or larger blisters.

• Actinic keratosis — This is a tiny bump that feels like sandpaper or a small, scaly patch of sun-damaged skin that has a pink, red, yellow or brownish tint. Unlike suntan markings or sunburns, an actinic keratosis does not usually go away unless it is frozen, chemically treated or removed by a doctor. An actinic keratosis develops in areas of skin that have undergone repeated or long-term exposure to the sun's UV light, and it is a warning sign of increased risk of skin cancer. About 10% to 15% of actinic keratoses eventually change into squamous cell cancers of the skin.

• Long-term changes in the skin's collagen (a structural protein) — These changes include photoaging (premature aging of the skin because of sun exposure) and actinic purpura (bleeding from fragile blood vessels beneath the skin surface). In photoaging, the skin develops wrinkles and fine lines because of changes in the collagen of a deep layer of the skin called the dermis. In actinic purpura, UV radiation damages the structural collagen that supports the walls of the skin's tiny blood vessels. Particularly in older people, this collagen damage makes blood vessels more fragile and more likely to rupture following a slight impact.

Over a lifetime, repeated episodes of sunburn and unprotected sun exposure can increase a person's risk of malignant melanoma and other forms of skin cancer. As a rule, if you have fair skin and light eyes, you are at greater risk of sun-related skin damage and skin cancers. This is because your skin contains less of a dark pigment called melanin, which helps to protect the skin from the effects of UV radiation.