skin disorders
Overview of Sunlight and Skin Damage
Natural protection
The skin undergoes certain changes when exposed to UV light, to protect against damage. The epidermis (the skin's uppermost layer) thickens, blocking UV light. The melanocytes (pigment-producing skin cells) make increased amounts of melanin, a brownish-colored pigment that darkens the skin, resulting in a tan. Tanning provides some natural protection against future exposure to UV radiation because melanin absorbs the energy of UV light and helps prevent the light from damaging skin cells and penetrating deeper into the tissues. Otherwise, tanning has no health benefits. Tanning for the sake of being tanned is hazardous to health (see sidebar Are Tans Healthy? ). Sensitivity to sunlight varies according to the amount of Overview of Skin Pigment in the skin. Darker-skinned people have more melanin than lighter-skinned people and therefore greater built-in protection against the sun's harmful effects. However, darker-skinned people are still vulnerable to sun damage and the long-term effects of exposure to UV light. Darker-skinned people are still vulnerable to sun damage and the long-term effects of exposure to UV light. The amount of melanin present in a person's skin depends on heredity as well as on the amount of recent sun exposure. Some people are able to produce large amounts of melanin in response to UV light, whereas others produce very little. People with blond or red hair are especially susceptible to the short-term and long-term effects of UV radiation, because they are not able to produce enough melanin. The melanin in their skin can also become distributed unevenly, resulting in freckling. People with Vitiligo have patchy areas of skin that have no pigment. People with 