Castor oil for hydrating dry skin?

Relatively thin, dry skin is characterised by limited elasticity and a high sensitivity to temperature changes. To the touch, dry skin often feels rough and tends to flake. Unlike dehydrated skin, dry skin is not lacking in water but in fat. This is due to a low production of sebum, one of the components of the hydrolipidic film. Dry skin lacks lipids, which makes the epidermis more susceptible to external aggressions and facilitates the evaporation of the water contained in the skin. The lack of flexibility and the significant fragility of dry skin makes it particularly prone to skin ageing.

Dry skin requires a tailored skincare routine, incorporating moisturising and nourishing ingredients, such as castor oil. Capable of strengthening the hydrolipidic film, it is indeed beneficial for dry skin. According to a study on skin explants, castor oil could reduce transepidermal water loss (TEWL). Indeed, an hour after application, a difference of 50 µg/cm2.h was observed between the skin on which castor oil was used and the one that received nothing. This difference was 40 µg/cm2.h after 24 hours. It thus appears that the topical application of castor oil significantly reduced water loss.

The hydrating and nourishing effects of the castor oil were also evaluated during a clinical trial involving 15 individuals with dry skin. Each volunteer was given a formulation based on castor oil and distilled water. A bioelectrical impedance analysis was used to provide numerical values representing the skin's moisture levels. According to the model used, a rate below 33% indicates very dry skin, a rate between 34% and 37% indicates dry skin, a rate between 38% and 42% signifies normal skin, and a rate above 43% shows hydrated skin. The results obtained ten days later are transcribed in the table below.

According to this study, the regular use of castor oil could be beneficial for dry skin. The moisturising and nourishing effects of castor oil can be explained by its biochemical composition rich in fatty acids. Indeed, this vegetable oil contains oleic acid, an unsaturated fatty acid known for its film-forming effects. Oleic acid is naturally found in sebum and an external supply through topical application helps to strengthen the hydrolipidic film. In addition, castor oil contains linoleic acid, an omega-6 capable of inserting itself between the corneocytes and strengthening their cohesion. Better organised, the corneal layer is less prone to water loss.

Thanks to the various fatty acids it contains, thecastor oil appears to be an ally for dry skin.

• ORENTREICH N. & al. A new in vitro method for transepidermal water loss: A possible method for moisturizer evaluation. Journal of the Society of Cosmetic Chemists (1988).

• KUMAR M. & al. A Review on Phytochemical Constituents and Pharmacological Activities of Ricinus communis L. Plant. International Journal of Pharmacognosy and Phytochemical Research (2017).

• HIDAYAH N. & al. The Influence of Combination of Castor Oil with Aquades on Increasing Moisture over a Dry Skin. 3rd UNJ International Conference on Technical and Vocational Education and Training (2018).