Sun Tanning
Sun tanning describes a darkening of the skin (especially of fair-skinned individuals) in a natural physiological response stimulated by exposure to ultraviolet (UV) radiation from sunshine or from artificial sources such as a tanning bed. With excessive exposure to ultraviolet, a sunburn can develop.
Cause and effect
Two different mechanisms contribute to the UV-induced darkening of the skin. Firstly the UVA-radiation generates oxidative stress which in turn oxidises pre-existing melanin. This leads to rapid darkening of already existing melanin. The second mechanism is the increased production of melanin (melanogenesis).[1] It is a reaction of the body to photodamage from UVB.[2] This melanogenesis is triggered by the same DNA damage that causes sunburn. Melanogenesis leads to delayed tanning. It first becomes visible about 72 hours after exposure.[1] The tan that is created 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 release of the pigment melanin into the skin 's cells after exposure to ultraviolet radiation. Melanin is produced by cells called melanocytes and protects the body from direct and indirect DNA damage absorbing an excess of solar radiation, which can be harmful. Depending on genetics, some people can darken quickly and deeply whereas others do not darken much at all.
The ultraviolet frequencies responsible for tanning are often divided into the UVA (315 to 400nm wavelength) and UVB (280 to 315nm wavelength) ranges.
UVB
triggers the formation of CPD-DNA damage (direct DNA damage) which in turn induces an increased melanin production[2] is more likely to cause a sunburn than UVA as a result of overexposure. The mechanism for sunburn and increased melanogenesis is identical.[3] Both are caused by the direct DNA damage (formation of CPDs) reduced by virtually all sunscreens in accordance with their SPF is thought to cause
Cause and effect
Two different mechanisms contribute to the UV-induced darkening of the skin. Firstly the UVA-radiation generates oxidative stress which in turn oxidises pre-existing melanin. This leads to rapid darkening of already existing melanin. The second mechanism is the increased production of melanin (melanogenesis).[1] It is a reaction of the body to photodamage from UVB.[2] This melanogenesis is triggered by the same DNA damage that causes sunburn. Melanogenesis leads to delayed tanning. It first becomes visible about 72 hours after exposure.[1] The tan that is created 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 release of the pigment melanin into the skin 's cells after exposure to ultraviolet radiation. Melanin is produced by cells called melanocytes and protects the body from direct and indirect DNA damage absorbing an excess of solar radiation, which can be harmful. Depending on genetics, some people can darken quickly and deeply whereas others do not darken much at all.
The ultraviolet frequencies responsible for tanning are often divided into the UVA (315 to 400nm wavelength) and UVB (280 to 315nm wavelength) ranges.
UVB
triggers the formation of CPD-DNA damage (direct DNA damage) which in turn induces an increased melanin production[2] is more likely to cause a sunburn than UVA as a result of overexposure. The mechanism for sunburn and increased melanogenesis is identical.[3] Both are caused by the direct DNA damage (formation of CPDs) reduced by virtually all sunscreens in accordance with their SPF is thought to cause
References: ^ An ecologic study of cancer mortality rates in Spa...[Int J Cancer. 2007] - PubMed Result ^ Childhood sun exposure influences risk of multiple sclerosis in monozygotic twins ^ Sardone, Susan. "European Nude Beaches and Clothing-Optional Resorts." About.com, 2008. ^ Diffey, B.L ^ Lowe, Nicholas J (1991). "Physician 's guide to sunscreens". ISSN 0824784960. ^ Ashwood-Smith MJ