Our longest days of sunlight are coming! As the days become longer the sun also become brighter, and more Ultraviolet (UV) light hits us. At the beginning of the season our skin is sensitive to sun exposure, and we may get a sunburn instead of a suntan.
So, what is suntan? Tan is a pigment that protects your skin from harmful UV rays. Sunburn prevention depends on this pigment: how much and how fast your skin can make it. Sunlight travels to Earth as a mixture of both visible and invisible waves. Long waves are the rainbow of colors and harmless to people. Shorter waves like Ultraviolet light are invisible but can cause problems. Solar UV radiation can be UVA or UVB (The sun's UVC is filtered out by the atmosphere and doesn't hit us.)
- UVA ( 315-400 nm) tends to cause tanning
- UVB (280-315 nm) can cause damage in form of sunburn
Shorter wave lengths have higher energy but do not penetrate as deeply into our skin. Most of the skin absorbs ultraviolet at 220-300 nm range which includes UVB. UVA can give rise to free radicals, which can cause damage to DNA. UV radiation from the sun is also reflected differently by different surfaces. Sand, for example reflects 20% of radiation, while snow reflects 90% of radiation. You get hit with more UV radiation standing outdoors in the snow than in a desert!
What does the skin do to protect us from the harmful UV rays? Skin defends us with a suntan. The tan is made by special cells, called melanocytes:
- Step 1- our eyes react to the sunlight. Sunlight stimulates the optic nerve, which activates our pituitary gland
- Step 2- the pituitary gland produce melanocyte stimulating hormone (MSH)
- Step 3- MSH flows through the bloodstream and reaches the special skin cells,
- Step 4- melanocytes produce pigments which help to protect skin from sunburn.
Melanocytes produce two different pigments: eumelanin (brown) and phaeomelanin (yellow and red). And think about it: wearing sunglasses could slow down your skin tanning!
Now you know a little more about a suntan: why and how it happens. In our next blog we will talk about sunscreen, sun damage and how to take care of over-exposed skin.
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Medically reviewed on 06/01/17