The science behind UV-protective hair formulas: challenges and strategies

Excessive sun exposure is one of the main causes of structural damage to the hair shaft. Wavelengths between 254–400 nm induce protein degradation in hair. UVB radiation leads to protein loss, while UVA causes colour changes. When amino acids absorb this radiation, they generate free radicals that damage hair proteins, particularly keratin. Protecting the cuticle is essential to maintain the hair shaft's integrity. This can be achieved by using haircare products containing UV filters and film-formers to coat the cuticle and shield it from damage, as well as by applying hydrating and nourishing treatments. Reducing direct sun exposure by wearing hats or scarves is also recommended. 

Chemical filters often offer narrow-spectrum protection, so combining several filters is needed to meet regulatory standards. Some organic UV filters, like Avobenzone, are also photo-unstable and can degrade under sunlight. Formulating a product that is both aesthetically pleasing, easy to apply, and non-greasy on hair remains a major challenge. 

I would say it’s just as challenging as skin care. They must be easy to apply, so consumers are willing to use it. The hair photoprotection products are primarily targeted to dyed hair, especially auburn pigments, and grey shades. They are usually based on silicones, antioxidants and quaternary chemical UV filters that have more affinity for negatively charged hair surface and present higher efficacy. Unfortunately, there are no regulated parameters, like for skin photoprotection, for efficacy evaluation of hair care products, which makes impossible to compare the results published in the literature. That’s why it’s essential for researchers to use experimental conditions that reflect real-life sun exposure, considering dose, irradiance, duration, temperature, and humidity. 

While SPF is measured as for skincare, hair protection is evaluated through indicators such as colour fading, dryness, and malleability (ease of combing on wet and dry hair). Some studies have used the hemispherical directional reflectance method. For example, one study using the 410-Solar Reflectometer assessed three hair sunscreen products and found that none of them provided the expected UV protection. In particular, dark hair showed the lowest reflectance and therefore the highest absorption of radiation across all wavelength ranges, due to its higher eumelanin content. However, this absorption does not equate to effective protection: the tested products did not improve reflectance, meaning they failed to shield the hair from radiation. These findings underscore the need for more effective and targeted formulations in hair photoprotection. 

They are basically the same. They both need UV protection, moisturisation and offer a shield protection (film former). Dark hair, thanks to its higher melanin content, offers better protection for both hair proteins (against denaturation) and the scalp. Nonetheless, physical protection like hats and scarves remains the most effective method. 

A healthy scalp is key to healthy hair. Therefore, delivery systems that target both the hair fiber and the follicle are very promising: they can help promote growth, reduce inflammation, and delay signs of hair ageing like thinning or colour loss. Several types of delivery systems like liposomes, niosomes, transfersomes, lipid nanoparticles, polymeric microparticles and nanoparticles could be the future of delivering actives to scalp and follicles.