Coconut oil to protect hair from the sun?

When hair is exposed to sunlight, it is common to notice the appearance of lighter highlights or a slight natural lightening, often associated with summer. However, behind this aesthetic effect lie chemical modifications of the hair fibre. UV rays can interact with hair proteins, particularly keratin, and trigger the oxidation of certain amino acids. This photodegradation gradually weakens the structure of the hair and can alter the disulphide bonds that ensure its mechanical strength. In addition, exposure to UV promotes the formation of free radicals, which are responsible for the oxidation of hair pigments and the degradation of protective lipids present in the cuticle. Over time, these processes can result in hair that is drier, duller and more fragile.

Many people have realised that it is important to protect their hair from summer-related damage and therefore turn to plant oils, particularly coconut oil.

Used for a long time in traditional hair care, coconut oil is valued for its nourishing and protective properties. Its high content of medium-chain triglycerides, particularly lauric acid, gives it a specific affinity with the hair fibre. Unlike certain vegetable oils that remain essentially on the surface of the hair, coconut oil can penetrate relatively easily into the hair fibre, which enables it to act within the core of the cortex rather than solely at the level of the cuticle.

An experimental study investigated the ability of different fatty acids to penetrate coloured hair and protect the hair fibre. The researchers compared hair treatments containing medium-chain fatty acids (C8, C10 and C12), long-chain fatty acids (C14, C16 and C18), as well as coconut oil and oil rich in medium-chain triglycerides (MCT). The results showed that medium-chain fatty acids penetrated the hair fibre significantly better than long-chain fatty acids. Coconut oil, which is rich in lauric acid (C12), exhibited a penetration capacity comparable to that of MCT oils. This increased penetration makes it possible to partially fill the microfissures in the hair fibre and reduce protein loss, thereby helping to strengthen the mechanical resistance of the hair.

Some studies have also suggested that coconut oil may possess a low level of photoprotective capacity, with an SPF ranging between 1 and 7. This indicates that it can absorb a small proportion of UV rays, but this protection remains very limited compared with that provided by conventional sunscreens.

That said, no scientific study currently demonstrates that coconut oil can genuinely protect hair from damage induced by sun exposure. While its emollient properties and its ability to penetrate the hair fibre may help to nourish the hair and limit dehydration, these effects do not amount to reliable protection against UV radiation. To preserve the health of the hair fibre during periods of intense sunlight, other protective measures remain essential.

• MOHILE R. B. & al. Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage. Journal of Cosmetic Science (2003).

• SARAF S. & al. In vitro sun protection factor determination of herbal oils used in cosmetics. Pharmacognosy Research (2010). 

• CHAUHAN A. & al. UV-blocking potential of oils and juices. International Journal of Cosmetic Science (2016).

• MARTINIAKOVÁ S & al. The real UVB photoprotective efficacy of vegetable oils: In vitro and in vivo studies. Photochemical & Photobiological Sciences (2021).

• AHN C. & al. Determination of penetration and protection of fatty acids in bleached hair according to the fatty acid chain length and the application to understanding the protective effects of MCT oil and coconut oil. Fashion and Textiles (2023).

• JIANG H. & al. Penetration of oils into hair. International Journal of Cosmetic Science (2024).