We constantly hear and read about the impact of UV radiations on our skin and about photo-aging, but have you ever wondered how photodamage can also impact your hair?
Before anything else, let’s get things straight: there is no hair SPF product on the market, it’s just not a thing. SPF is for the skin, and for the skin only. So for the scalp maybe, but not for the hair, which can actually seriously get damaged by UV radiations.
The hair is a non living part of our body, and unlike the skin when a sunburn occurs, it won’t send a message of pain when it suffers overexposure. As a consequence of accumulated photodamage, will become less manageable, weaker, thinner, more brittle and will have developed more split ends. Chronic overexposure can ultimately lead to aggravated hair loss.
The sun bleaches the hair
Melanin, a pigment also present in our skin and eyes, is the natural photoprotectant in hair. The lighter your natural hair color, the less pigment (melanin) in your hair, and consequently the less natural protection from UV rays.
UV radiations and visible light cause the degradation of melanin in the hair shaft, a phenomenon called photo-bleaching. That’s why our hair – especially light and blonde hair – lightens in the summer and it’s not exactly as good as we think it is. Hair color change is mostly the responsibility of UVA rays – the same rays that cause photo-aging on our skin.
Sunlight degrades the hair proteins
In addition, UVB rays – the same ones that allow us to make vitamin D when hitting our skin but that also create sunburn in case of overexposure – are responsible for another sort of photodamage on hair: hair protein loss (or more specifically the oxidation of proteins called thiols into sulfonic acid). As a result, the hair loses its softness, gets frizzy and tangled. This loss in protein can’t be repaired, despite all the expensive hair masks you might be using.
Is hair dye a photo-protective solution?
Hair dye acts as a passive photo filter attenuating the incident light, hence reducing the photodamage on the hair fiber protein. However, the sun's rays equally bleach both artificial and natural pigments, so the color in dyed hair will unfortunately fade or turn dull, all the same as non-dyed hair.
With all that in mind, it is clear - and not surprising - that sunlight can also damage the hair. As for the skin, the preservation of melanin, our natural photoprotectant, should be a priority, and this can be achieved by adequate and reasonable exposure to the sun. As always, overexposure is the problem, and you should avoid it at all time.