Can hair really be hydrated?

Once it emerges from the hair follicles, hair is not alive. It consists mostly of inert keratin filaments devoid of metabolic activity. However, this does not prevent hair from holding water, nor for this water to play an important role in its appearance, elasticity, and resistance to breakage.

Hydrating, or more precisely conditioning hair, involves preventing water from entering or leaving the fiber. To accomplish this, the cuticle scales must be properly smoothed. This specifically involves the systematic application of a conditioner after every wash. Indeed, using a conditioner flattens the cuticle scales along the hair shaft thanks to the cationic surfactants it contains. This treatment also increases the adhesion of the cuticular scales to the hair shaft, which enhances the hair’s light-reflecting properties and reduces friction between hair fibers.

It is also important to maintain the cuticle’s lipid barrier. This is where emollients and occlusive agents come into play. Vegetable oils, such as the coconut oil or the apricot oil, rich in fatty acids, can form a film on the fiber surface, thereby reducing water evaporation. Some studies have even shown that lauric acid, one of the main components of coconut oil, can penetrate the hair and mitigate both cuticle swelling caused by water and the stress this imposes on the hair fibers.

Other studies have examined the effect of nanoemulsions on the hydration of textured hair samples obtained from a woman. Some hair fibers underwent a bleaching process, with or without subsequent recoloring. For reference, a nanoemulsion is a mixture of two or more immiscible liquids in which one is finely dispersed in the other, forming droplets at the nanometer scale. Specifically, three nanoemulsions were studied: a control nanoemulsion, a version enriched with 7.5% coconut oil, and a third containing 7.5% coconut oil and 0.1% wine lees extract. These nanoemulsions were applied to the three hair types, and their hydration was then observed.