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sunburn,inflammation of the skin caused by actinic rays from the sun or artificial sources. Moderate exposure to ultraviolet radiationultraviolet radiation,
invisible electromagnetic radiation between visible violet light and X rays; it ranges in wavelength from about 400 to 4 nanometers and in frequency from about 1015 to 1017 hertz.
..... Click the link for more information. is followed by a red blush, but severe exposure may result in blisters, pain, and constitutional symptoms. As ultraviolet rays penetrate the skin, they break down collagencollagen
, any of a group of proteins found in skin, ligaments, tendons, bone and cartilage, and other connective tissue. Cells called fibroblasts form the various fibers in connective tissue in the body.
..... Click the link for more information. and elastin, the two main structural components of the skin, a process that results in the wrinkled appearance of sun-damaged skin. In addition, the sun damages the DNA of the exposed skin cells. In response, the cells release enzymes that excise the damaged parts of the DNA and encourage the production of replacement DNA (a process that can go wrong and result in skin cancerskin cancer,
malignant tumor of the skin. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Rarer forms include mycosis fungoides (a type of lymphoma) and Kaposi's sarcoma.
..... Click the link for more information. ). At the same time, the production of melaninmelanin
, water-insoluble polymer of various compounds derived from the amino acid tyrosine. It is one of two pigments found in human skin and hair and adds brown to skin color; the other pigment is carotene, which contributes yellow coloring.
..... Click the link for more information. increases, darkening the skin. Melanin, the pigment that gives skin its color, acts as a barrier to further damage by absorbing ultraviolet light. A suntan results from this attempt by the skin to protect itself. Light-skinned persons and infants are especially susceptible to ultraviolet rays because they lack sufficient protective skin pigment. Certain diseases and drugs may also increase photosensitivity.
Due to the increase in the incidence of skin cancer and the effects of ozone layerozone layer
region of the stratosphere containing relatively high concentrations of ozone, located at altitudes of 12–30 mi (19–48 km) above the earth's surface.
..... Click the link for more information. depletion, more attention is being placed on protecting the skin from the sun's ultraviolet rays with broad spectrum sunscreens or clothing. Broad spectrum sunscreens block both UVA and UVB rays (two of the three bands of ultraviolet radiation). The relative UVB protection of a sunscreen is indicated by its SPF (sun protection factor) number. A higher number indicates a sunscreen that is more effective in preventing sunburn, but it is UVA radiation that is more likely to cause cancer and skin aging. A broad spectrum sunscreen with an SPF of 30 or higher is generally recommended by dermatologists. Some products may contain opaque formulations of zinc oxide or titanium dioxide that physically block all rays.