Sunlight is the single most important sourse of UV radiation exposure to human skin.Light between wavelengths of 200nm to 400nm is called UV radiation.The response of the skin to sun exposure include Vitamin D synthesis , tanning , sunburn , aging , and predisposition to skin cancers.Vitamin D synthesis is a useful response while the rest of them are harmful responses.
Tanning is a response of the skin to UV-A radiations.Lighter the complection more it gets tanned.It is a result of incresed production of melanin (skin pigment) producing cells as well as increased activity of the already existing ones.
Sunburn on the other hand is response of the skin to UV-B radiations.The exposed area becomes red and painful and may develop peeling and pigmentation by the next day.Sunburns can be prevented by using a good sunscreen.
Aging-Yes sunlight can make you grow older!It is because of the degenative changes skin develops wrinkles and irregular pigmentation.
UV Rays can damage the DNA of skin cells to induce cancers.
How should we protect our skin?
We can protect the skin by using sunscreens.Sunscreens are of two types:
CHEMICAL SUNSCREENS:Chemical sunscreens work by absorbing the harmful rays of sun but allow tanning to occur.The efficacy of a suncreen is conveyed by its SPF value.SPF stands for Sun Protection Factor.It is defined as the ratio of the dose of UVB radiation that will produce minimal erthyma(redness) on protected skin to the dose required for the same on unprotected skin.Para amino benzoic acid,benzophenones and cinnamates are found in chemical sunscreens.
PHYSICAL SUNSCREENS:these are thick lotions or creams that may be cosmetically disagreeable.They are different from chemical sunscreens because they protect from both sunburn as well as tanning.Zinc oxide,titanium oxide are found in physical sunscreens.
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