But what exactly is tanning? By what mechanism does our skin obtain this tanned complexion? Focus on the holy grail of summer!
The mechanisms of tanning
As we saw in the previous article on the skin, it is composed of an epidermis (superficial) and a dermis (deep layer). It is the cells of the epidermis that tan. In the epidermis there are specialized cells at the origin of our tan: the melanocytes. Under the effect of UV rays, the cells will increase the production of a colored pigment: melanin . The capture of UV by melanin (which will oxidize) allows radiation to be stopped in its progression and therefore to protect the deep and fragile layers of the skin . Subsequently, the melanin is expelled by the melanocytes and will color the neighboring cells of the epidermis, at the origin of our pigmentation.
There are two types of UV in solar radiation:
UVA rays : they cause rapid pigmentation (about a minute) but will also disappear quickly. It is therefore not really this type of radiation responsible for tanning but allows you to obtain an “evening tan”. This radiation burns little (1000 times less than UVB).
UVB rays : they are responsible for our famous tan. It will appear about two days after our exposure to the sun to reach a maximum around the 20th day then, will gradually disappear if no other exposure appears.
Unfortunately, the rays that produce the tan are also the ones that burn the most. UVB burns 1000 times more than UVA, and makes you tan 1000 times more.
Why does the tan disappear?
Since the tan is located on the cells, the keratinocytes, of the epidermis and these are renewed approximately every thirty days, it will naturally and gradually disappear. Indeed, one month after the last rays of sunshine, the skin will be totally regenerated and therefore, there will be no more traces of tanning.
Be careful though, the fact that the cells take a month to renew itself does not mean that the tan necessarily lasts a month. Indeed, the fact of peeling will make the tan disappear more quickly and conversely, a well hydrated skin will prolong this tan.
Sunburn and easy to tan? What are the differences by skin type?
And yes, light and dark skin will not have the same tendency to tan and have sunburn. But what are these differences related to? Each individual, depending on their genetics, will produce more or less melanin, thus causing a difference in the way they tan.
For very fair skin, the majority of the skin will produce red pigments: the pheomelanin, which does not protect against the sun's rays. Conversely, dark skin will have a majority of brown pigment, theeumelanin which effectively protects against radiation.
Be careful though, for dark skin, it is only a partial protection, so always make sure to use protection adapted to the exposure.
There you go, you know all the secrets of tanning!