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Science behind sun damage to hair

By August 1, 2019 Chemicals, Hair health

We decided to take a plunge this August and dive in to understanding how sun damage works when it comes to hair health. Before we dive in, let’s quickly recap what is SPF, what is UV rays, the difference between UVA, UVB and UVC (and uncovering the reasons why we don’t get to read much about those).

SPF

The SPF denotes “sun protecting factor” – meaning the amount of rays the sunscreen block. E.g. SPF 15 means, that 1/15th of the burning radiation will reach the skin, assuming sunscreen is applied evenly at a thick dosage of 2mg per square centimeter. Similarly, SPF 60, means that only 1/60th of the same radiation will reach the skin or hair.

Deciphering UVA, UVB and UVC (!)

Ultraviolet (UV) ray is a band of the electromagnetic spectrum with a specific wavelength: from 10nm to 400nm. This means that UV rays stand somewhere between visible light which human eye is able to see, and much shorter in length, X-rays. UV radiation is present in sunlight, contributing to about 10% of the total output of the Sun. UV are strong enough to cause chemical reactions in compounds, including fluorescence, strengthening the bones in mammals and various photo effects achieved by photons, particles of light.

Finally, the difference between UVA, UVB and UVC rays is the length of the electromagnetic wave. UVA 400-320nm and UVB is 320-290nm. Therefore sunscreens with a “broad spectrum” are those which cover various lengths of UV-rays. UVA accounts to 95% of all the UV radiation reaching Earth’s surface. While UVB proportion is much, much smaller. UVC rays, however get absorbed by Earth’s ozone layer and therefore are not something we consider in this overview.

Effect of UV on hair

Hair shaft is a nonliving cell and, therefore, unlike skin cells, requires no protection from carcinogenesis commonly caused by ultraviolet (UV) radiation on skin – because carcinogenesis in a hair shaft itself is not currently considered possible. If hair proteins in the shaft are altered by sun exposure, damaged hair can be removed and replaced by new growth.

However, UV radiation damages hair lipids, so photodamaged hair is dry and dull, as sunlight damages disulphide bonds – the protein links that creates elasticity and essentially “holds your hair shaft together”. In addition, colour treated hair, already deprived of its natural moisture is more likely to dry and become brittle after exposure to the sun. Hair devoid of natural lipids, is subject to static electricity, fractures easily and appears frizzy.

Vulnerability of colour-treated hair

Human hair naturally contains two pigments: eumelanin and phenomelanin. Both are accountable for brown/black and red/yellow hues in our hair respectively and both get affected by UV rays. Another melanin, called oxymelanin, is found in unprocessed human hair which has been exposed to the sun. It is the similar compound found in bleached hair, as well. The amount of oxymelanin affects the value of the hair as well as causing photo-ageing. This leads to natural “summer highlights” amongst those of us with untreated virgin hair.

How do sunscreens work?

UV-screens create a barrier to the UVA and UVB rays. While the most common ingredients of sunscreen is titanium dioxide and zinc oxide, there are other protecting ingredients that create the barrier which either absorbs, reflects or scatter harmful UV rays.

Sunscreens tend to also use heavier carrier oil to spread the UV-ray absorbing molecules across the skin or hair, thus making it more difficult to wash off but increasing its water-resistance. This is something to be mindful of if you don’t want to weight down your hair.

What about scalp?

As far as your scalp is concerned – while some UV rays can be healing to eczema and psoriasis, because UV-radiation can cause carcinogenesis in skin cells, during sun exposure, it is advised to protect your scalp: whether by applying sunscreen or wearing a hat with sufficient SPF protection.

Ecotoxicity

Some sunscreen compounds, such as octyl methoxycinnamate have been found to damage coral reefs, however while titanium dioxide and zinc oxide are not found directly damaging to those, the nanoparticles of these compounds end up in soil as well as negatively impact marine life. So if you are an eco warrior, like us – opt for wearing a wide-brimmed sun hat or a head scarf to protect your locks from damaging UV radiation.

Sun-protection is on-trend in 2019!

It is lucky, however that this summer 2019 hair trend is hair accessories and top-knots, and here is why we’re excited about it when it comes to protecting your hair from the sun.

Putting your hair up in a top-knot will ensure that less of your hair shafts is exposed to UV-rays, therefore protecting you from brittleness, and hair discolouration – whether from natural or artificial pigments in your hair – if you have coloured hair to begin with.

The best thing you can do to your hair to protect it against UV radiation is to wear a fabulous wide-brimmed hat, which would also help protect the skin on your face as well. Else, you can opt for headscarves and other hair protective accessories to ensure you don’t have to spend a fortune and heaps of time at the end of summer resuscitating your hair locks from those summer holidays.

Needless to say, that opting for physical barrier, such as a hat or a headscarf is much better for your body as you’re not lathering yourself with chemicals, as well as beneficial to the mother nature. Needless to say… a sun hat can also be much, much affordable investment in your hair health, too.

Sources:

Sunscreens and Hair Photoprotection, https://www.derm.theclinics.com/article/S0733-8635(05)00105-1/fulltext

Sunscreens: Development: Evaluation, and Regulatory Aspects: Second Edition, https://books.google.com/books?hl=en&lr=&id=kv67G9uYC28C&oi=fnd&pg=PA445&dq=hair+and+sunscreen&ots=DDGSUhWHlo&sig=4sGYqabMXYny_6jn8-EUL7N9eJg#v=onepage&q=hair%20and%20sunscreen&f=false

Wikipedia on Ultraviolet, https://en.wikipedia.org/wiki/Ultraviolet

The Difference Between UVA, UVB, and UVC Ray, https://share.upmc.com/2014/07/infographic-abcs-uv-difference-uva-uvb-uvc/

UVA & UVB, https://www.skincancer.org/prevention/uva-and-uvb

Wikipedia on Melanin, https://en.wikipedia.org/wiki/Melanin

Hazardous Effects of Titanium Dioxide Nanoparticles in Ecosystem, https://www.hindawi.com/journals/bca/2017/4101735/

Effects of zinc-oxide nanoparticles on soil, plants, animals and soil organisms: A review, https://www.sciencedirect.com/science/article/pii/S2215153217302404

Establishment of keratinocyte cell lines from human hair follicles, https://www.nature.com/articles/s41598-018-31829-0

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