People often wonder why their skin darkens and the darkening I am talking about here are different hues of tans and browns and mostly all of them are caused simply be injury to the skin. Whether the injury is from the ultraviolet light from the sun, or the heat from a cooking burn, or even just a scratch on your arm or leg the common theme here is injury. Why does the skin darken, darkening is one of two different defense mechanisms that the skin has. The other is one by the way is thickening. So you will often get a callous from a shoe rubbing, or a handle of a tennis racket, or a golf club that repetitively rubs and the thickening there is to protect the skin from the rubbing so it does not tear, but what protect does darkening offer to the skin. The darkening actually makes sense for protection from the ultraviolet injury from the sunlight, because the darker the skin gets the less ultraviolet light which is damaging the less ultraviolet light can get into the skin.
We know as a matter of fact that medium toned African American skin has an intrinsic built-in SPF of 15 or 16. So the darkening is protective against the ultraviolet injury. But what about an injury from a heat burn or an injury from a scratch, on a evolutionary prospective it really does not make any sense to us, however the skin is not that smart and it treats all of these injuries the same. But your take away is if you are seeing darkening areas on your skin, whether they are small areas or large areas your skin is pleading with you “please take better care of me.”