Why use a hair oil?

Thehair oil is a concentrate of lipids, whose main role is to hydrate and nourish the hair. Generally rich in vegetable oils, it forms a lipid veil on the surface of the hair fibres, reinforcing the hydrating and protective action of the hydrolipidic film. Hair oils thus limit the dehydration of the fibres and prevent any "straw-like hair" effect.

Furthermore, most oils are formulated to penetrate the hair fibre and insert themselves between the scales of the cuticle, the outermost layer of the hair. Indeed, they serve to strengthen the intercellular cement and restore cell cohesion. This property of hair oils comes from their richness in fatty acids. Having a chemical structure similar to that of the lipids in the cuticle, they can easily insert themselves through biomimicry. When the hair scales are well aligned and structured, the hair gains in elasticity and softness.

A recent study conducted with certain plant oils, often found in the composition of hair oils, examined their ability to improve fibre strength. After seven days of daily application, the results showed that hair treated with olive oil and Brazil nut oil exhibited an increase in breakage strength and a reduction in combing force. It thus appears that plant oils, and by extension hair oils, are interesting treatments for hair care.

All hair types can benefit from the advantages that hair oils have to offer, particularly dull and lacklustre hair. Indeed, as mentioned earlier, oils nourish the hair fibres and strengthen the intercellular cement of the cuticle. They thus help to restore the alignment of the scales. Now, when the structure of the hair fibre is robust and the scales forming its cuticle are correctly bonded, the hair appears shinier, as they are capable of reflecting light. Regular application of a hair oil can therefore be beneficial for reviving the shine of one's hair.

It should be noted that the study by CAMPOS, previously mentioned, also evaluated the shine of fibres after daily application of vegetable oils for seven days. The results indicate an overall increase in hair shine, although precise quantitative data is not available. Several other scientific studies report on the ability of vegetable oils to enhance hair shine.

Hair is subjected all year round to various external factors that weaken it: the heat of the hairdryer, UV rays, pollution, swimming pool chlorine, sand and sea salt... These different elements can damage the structure of the hair fibres, alter their colour and promote the occurrence of split ends, each to their own extent. By reinforcing the hydrolipidic film that naturally coats the hair, hair oils form a first line of defence between the fibres and environmental aggressions.

The protective action of coconut oil, a vegetable oil sometimes used to formulate hair oils, has been demonstrated in a study. This research highlighted that its application before and after the shampoo significantly reduced the protein loss from hair, whether it was intact or damaged. By coating the fibres with a film and penetrating the cuticle, the lipids contained in hair oils protect the hair scales from the detergent agents present in most shampoos.

Furthermore, hair oils are often formulated with antioxidant plant oils. They can thus help to combat oxidative stress, which is harmful to the fibres. Indeed, free radicals attack various components of the hair, such as the lipids of the cuticle, but also proteins like keratin and melanin. These oxidative damages cause a loss of strength and elasticity in the hair, making it drier and more prone to breakage. To protect them, it is recommended to use a hair oil once or twice a week, according to the instructions provided on the care product.

Hair oils can finally be used as a daily styling treatment by individuals with textured hair, that is, wavy, curly or frizzy hair. Indeed, by reforming the hair's natural lipid barrier, these products help to retain moisture within the fibres, making the hair less prone to frizz. Furthermore, hair oils enhance the elasticity of the hair and promote its resistance to stretching and its ability to regain its natural shape after deformation. They are therefore frequently used to help define curls.

Indeed, by providing intense hydration to the hair and strengthening its structure, they allow curls to form more easily and maintain their shape throughout the day, thereby reducing the need for additional styling products. For individuals with textured hair, hair oils serve multiple functions: they protect the fibres, impart softness and shine, and enhance their hold.

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

• CAMPOS P. & al. Development and efficacy evaluation of hair care formulations containing vegetable oils and silicone. International Journal of Phytocosmetics and Natural Ingredients (2018).

• MESINKOVSKA N. & al. Coconut, castor, and argan oil for hair in skin of color patients: A systematic review. Journal of drugs in dermatology (2022).