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the darkening of human skin after exposure to ultraviolet radiation; such exposure causes an excess of the pigment melanin to be deposited in the surface layers.
A suntan develops gradually after repeated exposure to ultraviolet rays of low intensity. The deepest and longest-lasting tan results from prolonged exposure to sunlight; it often has an adverse effect on health (on the nervous, cardiovascular, and other systems). The extent and rapidity with which tanning takes place are not indicators of health.
Sensitivity to ultraviolet radiation varies from person to person, especially in children. Brunets with a swarthy skin tan more quickly than blonds or redheads with delicate, tender skin, which often burns on exposure to ultraviolet rays. Applying vegetable oils (nut, peach, and so forth) to skin speeds the tanning process and prevents the skin from drying out and, to some extent, from burning.