How to protect your hair from UV radiation?

Tip No. 1: Use a sunscreen on your hair.

To limit sun damage to hair, some hair-care products contain chemical filters, including protective sprays, UV mists and hair serums. As when applied to skin, the organic filters can absorb UV rays and convert light energy into heat, preventing UV rays from damaging the hair fibre.

Among the UV filters most used to formulate hair products providing UV protection are ethylhexyl methoxycinnamate, ethylhexyl salicylate, avobenzone and ensulizole. These molecules adhere poorly to the hair fibre. Hair carries a negative surface charge (its isoelectric point is around 3.7), which prevents neutral molecules from binding effectively. They are removed by wind and sweat. To address this problem, it is preferable to use cationic filters, which have a natural affinity with the hair surface. Examples include cinnamidopropyltrimonium chloride and dimethylpabamidopropyl laurdimonium tosylate.

Tip No. 2: Incorporate antioxidants into your summer hair-care routine.

Sunlight does more than damage hair proteins: by generating reactive oxygen species within the fibres, it drives oxidation of lipids, pigments, and keratin. To limit these effects, antioxidants may be beneficial as they can trap free radicals before they harm the hair structure. Some scientific reviews report that complexes based on grape seed procyanidins, vitamin E and rosemary extracts have demonstrated efficacy in hair formulations applied before sun exposure. Other plant extracts have shown activity, such as artichoke extract, rich in hydroxycinnamic derivatives that limit lipid peroxidation and protein degradation, and Japanese honeysuckle extract, containing quercetin, a flavonoid with potent antioxidant capacity.

Tip No. 3: Opt for products containing hydrolysed keratin.

Keratins are large proteins that may have difficulty penetrating the hair fibre. To address this, they can be hydrolysed, that is, broken into smaller fragments. Hydrolysed keratin is now a common hair care ingredient that, according to a recent study, may help protect hair from sun exposure. In the research, scientists treated hair strands with a solution containing hydrolysed keratin and then exposed them to irradiation in an accelerated-ageing chamber for six days at 35 °C and 60 % humidity. Untreated hair served as the control.

Mechanical test results are unambiguous: in unprotected hair, tensile strength falls by 14.32%, a classic sign of structural degradation. By contrast, hair pre-treated with hydrolysed keratin retains mechanical integrity and shows improved properties: after irradiation, its Young’s modulus—which reflects fibre stiffness—increases by 21.66%. Before exposure, treated hair had characteristics similar to the control group. These findings suggest that hydrolysed keratin can act as a structural reinforcement against UV.

Hydrolysed keratin acts in two stages to protect hair. Once applied to the fibres, it forms a protective film that partially absorbs solar radiation. Nonetheless, throughout exposure, this protective layer degrades, releasing lower-molecular-weight peptides capable of penetrating the cortex, the inner region rich in fibrous keratin. Once inside, these fragments reinforce weak bonds between natural keratin chains, thus improving the hair’s overall mechanical strength.

Tip No. 4: Use protective silicones.

Often criticised for their polluting effect, the silicones can protect hair exposed to sunlight. These polymers can form a film on fibre surfaces, which eases styling, increases shine, limits water loss, and creates a barrier against environmental stressors such as UV rays. In a recent study, trimethylsiloxysilicate, a silicone, helped retain about 11% of colour in blonde-dyed hair exposed to intense artificial light. In another study, a non-ionic silicone emulsion protected up to 83.5% of colour and 72% of shine in auburn hair. Silicone performance depends on its ability to adhere to the hair fibre. Cationic silicones show higher efficacy due to the hair surface's natural negative charge.

Tip No. 5: Wear a hat, cap or scarf.

The most effective sun protection remains a physical barrier. Wear a wide-brimmed hat, headscarf or cap to limit direct UV exposure to the hair between 11:00 and 16:00, when solar intensity peaks. This protection is essential for light, white, bleached or dyed hair, which has increased sensitivity to photodegradation.

Tip No. 6: avoid exposing wet hair to sunlight.

It can be tempting on a sunny day to let hair air-dry outdoors after a swim. However, when wet, hair is more vulnerable. Water saturating the hair fibre causes a cuticle dilation and scale separation, exposing the cortex. UV rays can then penetrate the hair more easily and damage its structural proteins and protective lipids. To reduce these effects, we advise shielding wet hair from the sun. After a swim in the sea or pool, pat it dry with an absorbent towel then cover it with a hat or scarf. This simple action can make a difference for coloured, bleached or porous.

Tip No. 7: Use an after-sun.

Even when hair is protected in advance, it undergoes a significant stress after prolonged sun exposure. Applying an after-sun hair treatment, often in the form of a mask, balm, spray or cream, can therefore be beneficial. These formulations act on several fronts. In addition to rehydrating hair using humectants such as glycerin or aloe vera, after-sun products include film-forming agents that strengthen cuticle cohesion and improve fibre mechanical resistance, such as plant oils. Finally, most contain antioxidants to prevent chain oxidation which can continue to weaken hair in the hours following UV exposure.