Sunburn is simply a burn or erythema (reddening) and oedema (swelling) on your skin from excessive exposure to the sun's rays, more specifically the ultraviolet (UV) radiation that is emitted from the sun. Sunburn may also occur from exposure to other UV light sources such as solaria or tanning salons.
At a cellular level, sunburn is associated with microscopic changes in the skin. There is the formation of UV induced sunburn cells and a reduction in Langerhan cells and mast cells, which play an essential part of the body's immune defence system.
To better understand the causes of sunburn we need to take a look at some basic principles of the electromagnetic (light) spectrum. This spectrum is divided according to wavelength into ultraviolet (<400nm), visible (400-760nm), and infrared (>760nm). The ultraviolet (UV) spectrum is further divided into 3 broad areas:
* Ultraviolet A (UV-A) = 320-400nm
* Ultraviolet B (UV-B) = 290-320nm
* Ultraviolet C (UV-C) = <290nm
UV-C radiation is filtered out or absorbed in the outer atmosphere so does not pose a problem to humans. It is UV-A and UV-B radiation that are the primary causes of sunburn. Although both wavelengths are implicated in sunburn, the skin reacts differently to each one.
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