How to protect your hair from sun exposure?

Tip No. 1: Use a sunscreen formulated for hair.

To limit the sun’s effects on hair, some hair care products now include chemical filters, such as protective sprays, UV mists, and hair serums. As on skin, organic filters can absorb UV rays and convert light energy into heat, preventing UV rays from damaging the hair fiber.

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

Tip No. 2: Integrate antioxidants into your summer hair routine.

Sunlight does not only damage hair proteins: by generating reactive oxygen species within the fibers, it drives lipid, pigment, and keratin oxidation. To limit these effects, antioxidants can help because they can trap free radicals before they damage the hair structure. Some scientific reviews mention that complexes based on grape seed procyanidins, vitamin E and rosemary extracts have shown efficacy in hair formulations applied before sun exposure. Other plant extracts have also proven effective, such as artichoke extract, rich in hydroxycinnamic derivatives that limit lipid peroxidation and protein degradation, or Japanese honeysuckle extract, containing quercetin, a flavonoid with high antioxidant activity.

Tip No. 3: Use products containing hydrolyzed keratin.

Keratin is a large protein that may struggle to penetrate the hair shaft. To address this, it can be hydrolyzed into smaller fragments. Hydrolyzed keratin is a popular hair care ingredient and, according to a study, may help protect hair from sun exposure. In this research, scientists applied a hydrolyzed keratin solution to hair strands and exposed them to irradiation in an accelerated aging chamber for six days at 35°C and 60% humidity. Untreated hair served as the control group.

Mechanical test results are clear: unprotected hair shows a 14.32% decrease in tensile strength, a sign of structural breakdown. In contrast, hair treated with hydrolyzed keratin maintains mechanical integrity and shows improved properties: after UV exposure, its Young’s modulus—reflecting fiber stiffness—increases by 21.66%. Before exposure, treated hair had characteristics similar to the control group. These results suggest that hydrolyzed keratin can act as a structural reinforcement against UV radiation.

Hydrolyzed keratin protects hair in two phases. Applied to the fibers, it forms a protective film that absorbs some solar radiation. During exposure, that layer degrades, releasing lower-molecular-weight peptides able to penetrate the cortex, the inner zone rich in fibrous keratin. Inside, these fragments reinforce weak bonds between natural keratin chains, improving the hair’s mechanical strength.

Tip No. 4: Use protective silicones.

Often criticized for their environmental impact, silicones can protect hair exposed to sunlight. These polymers can form a film on the fiber surface that eases styling, boosts shine, limits water loss, and creates a barrier against environmental stressors, including UV rays. In a recent study, trimethylsiloxysilicate preserved 11% of the color in blonde dyed hair exposed to intense artificial light. In other work, a nonionic silicone emulsion preserved up to 83.5% of the color and 72% of the shine in auburn hair. The efficacy of silicones depends on their ability to adhere to hair fibers. Cationic silicones perform best due to the natural negative charge of hair surfaces.

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

Primary protection against sun exposure is the physical barrier. Wearing a wide-brimmed hat, a scarf, or a cap reduces direct UV exposure to hair between 11 am and 4 pm, when solar intensity peaks. This measure is essential for light, white, bleached, or tinted hair, which is more sensitive to photodegradation.

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

It may be tempting on a sunny day to let your hair to dry outdoors after a swim. However, when hair is wet, it’s more vulnerable. Water that penetrates the hair fiber causes a swelling of the cuticle and lifting of the scales, leaving the cortex exposed. UV rays can then penetrate the hair more easily and damage its protective proteins and lipids. To reduce these effects, we recommend protecting wet hair from the sun. After swimming in the sea or in a pool, pat hair with an absorbent towel and cover it with a hat or scarf. This simple step can make a difference, especially for colored, bleached, or porous.

Tip No. 7: Use an after-sun product.

Even with prior protection, hair undergoes a significant stress after prolonged sun exposure. Applying an after-sun hair treatment, often in the form of masks, balms, sprays, or creams, can be a useful step. These formulas act on several levels. In addition to rehydrating hair with humectants such as the glycerin or the aloe vera, these treatments contain film-forming ingredients such as plant oils that strengthen cuticle scale cohesion and improve fiber mechanical strength. Most also include antioxidants to prevent chain-oxidation which can continue to weaken hair in the hours following UV exposure.