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There are two types of rays emitted by the sun which can cause
tanning- UVA and UVB. It is the ultraviolet A (UVA) rays which are
responsible for much of the tanning and skin aging and can lead to a
dangerous type of cancer known as melanoma. Usually the sunscreens offer
very little or almost no protection against these rays although clothing
is supposed to offer some kind of protection. It is present more
uniformly throughout the day as compared to the ultraviolet B (UVB) rays.
The
UVB rays on the other hand can also lead to certain forms of cancer,
skin aging (although, considerably slower as compared to UVA), wrinkles
and moles as well. Yet moderate exposure to these rays is beneficial to
the body. Almost all the sunscreens offer protection against the UVB
rays.
There are also UVC rays which are present
in the environment. But, they get filtered out and never reach us.
The
melanocytes actually produce two different kinds of pigments- eumelanin
and phaeomelanin. It is the eumelanin which is responsible for giving
the tanned look. The redheads produce more of phaeomelanin which is why
they don't get tanned quite easily. As for the Albinos, because of lack
of an enzyme called tyrosinase, the melanin-producing pathway is blocked
and thus, they do not have any pigment in their hair, skin or even
irises.
Though, tanning is actually a mechanism of the body which
protects it against the harmful UV rays. But as excess of anything is
bad, so overexposure to the sun is also harmful.
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