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Sun tanning, also called bronzing, is the act of exposing the skin to ultraviolet (UV) radiation, for the goal of darkening skin color, either for the period of sun bathing or utilizing artificial sources, such as tanning beds.
 Tanning
Tanning is a natural method, whereby the skin creates the brown-colored pigment named melanin, to shield it against the unsafe UV rays in sunlight, but operates uniformly with artificial UV radiation. There are two different mechanisms involved.
First, the UVA-radiation produces oxidative stress, which in turn oxidises pre-existing melanin. This leads to instant darkening of already existing melanin. Secondly, there is an increased production of melanin .It is a end result of the body to photodamage from UVB. This melanogenesis is triggered by the same DNA damage that causes sunburn. Melanogenesis leads to delayed tanning. It initially becomes visible about 72 hours after contact.The tan that is formed by an increased melanogenesis lasts much longer than the one that is caused by oxidation of existing melanin.
Darkening of the skin is caused by an increased emission of the pigment melanin into the skin's cells following exposure to ultraviolet radiation. Melanin is produced by cells called melanocytes and guards the body from direct and indirect DNA damage absorbing an additional of solar radiation, which can otherwise be harmful. all depends on a person's hereditary profile, some people can darken fast and deeply whereas others do not darken much at all.
The ultraviolet frequencies responsible for tanning are regularly divided into the UVA and UVB ranges.
There are several options to have a nice skin tanning like creams and lotions.
>References:
http://en.wikipedia.org/wiki/Sun_tanning
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Sun Tanning
