Sun and skin: UV radiation and skin phototypes
(Image of Sunrise - MrShemp - All Rights Reserved)
Humans are able to see electromagnetic rays from 400 nm to 750 nm as light. Below 400 nm, there are ultraviolet rays, above 750 nm, it is called infrared light. The ultraviolet radiation of the sunlight is divided into 3 different categories, based on the wavelength, with different physical and biological effects:
UVA - 315 to 400 nm
UVC - 100 to 290 nm
UVA rays make up 98 percent of the UV rays. They are very dangerous for our skin, because they penetrate very deeply into the dermis causing premature skin aging by generating free radicals and affecting collagen and elastin. Also skin cancer can emerge from UVA rays.
UVB rays make up only 2 percent of the UV radiation, but they are very energetic. On the skin, they activate the pigmentation processes (browning). But they are also responsible for inflammatory processes (sunburns, erythema) and for the development of skin cancer.
UVC radiation is almost completely absorbed by the ozone layer and does not affect the skin.
The skin phototypes
Type I - extremely at risk, needs very high sun protection very fair, many freckles, red or blonde hair, always burns, never tans natural self-protection time*: 5 to 10 minutes
Type II - sensitive skin, needs high to very high sun protection fair, few freckles, blonde to brown hair, burns easily, rarely tans natural self-protection time: 10 to 20 minutes
Type III - common sensitive skin, needs high sun protection fair to light brown skin, dark blonde or brown sometimes burns, normally tans natural self-protection time: 20 to 30 minutes
Type IV - little sensitive skin, needs protection for tanned skin brown to olive skin, no freckles, brown or black hair
* = exposure time in sunlight of unprotected skin without sunburn
Information courtesy of BeautyPress.com - All Rights Reserved.
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