We’ve all experienced the effects of prolonged sun exposure. Whether we are laying in a tanning bed or are out sunbathing on a beach, our complexion darkens when exposed to intense UV rays. Curiously though, it does the opposite to our hair. What process cause sunlight to darken our skin, but lighten our hair?
What happens when you tan?
UV rays from the sun or a tanning bed will trigger the production of melanin your skin. Melanin is the brownish-black pigment that help filter out harmful ultraviolet rays. The production of more melanin is a response from your skin to help fight off and minimize the effects of the Sun’s dangerous rays.
It is a relatively quick response that can happen over a period of hours to a couple of days. The response is tougher to see on lighter skinned people but is more obvious with people with darker skin.
The second (and slower) reaction of our skin cells to intense UV radiation is called ‘delayed tanning’. As the name suggests, it is much slower and drawn out process. The scientific term for the reaction is called melanogenesis.
Melanogenesis is the process in which cells are ramping up the production of melanin pigment. In addition to creating more overall melanocytes, the genes responsible are producing much darker versions. When you have more melanocytes in your skin, melanocytes which are much darker than the previous ones, your skin becomes darker – you get tanned.
What about hair?
The melanin in our hair that give it its color is dead. Your hair cannot produce melanin itself, so once it leaves the follicle, it’s more or less inert. It remains inert until some outside force acts upon it – like hair dye or sunlight. When your hair is subject to long periods of intense sunlight, your hair gets lighter because the UV rays breakdown the melanin molecules into simpler, much less colorful compounds.
However, the exact mechanism by which this is accomplished is not entirely clear. “The ionic pathway probably begins by nucleophilic attack of the peroxide anion on the o-quinone grouping,” says one research text. The melanin in both skin and hair is meant to protect the other tissue, but in the skin it’s renewed (the skin gets darker) whereas in our hair, it’s not.
While a tanned complexion can certainly be appealing to the eye, just remember the reason why your body is getting tanned in the first place. To protect you.