The oxidation of fatty acids is a natural phenomenon often overlooked that could potentially impair the skin barrier and exacerbate water loss. How do fatty acids oxidise? Does this process impact skin hydration? Discover all the answers below.
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The oxidation of fatty acids exacerbates dehydration.
Summary
- How does the oxidation of fatty acids occur?
- Does the oxidation of fatty acids lead to skin dehydration?
- Sources
Published March 17, 2025,
updated on March 17, 2025,
by
Pauline, Chemical Engineer
—
6 min read
How does the oxidation of fatty acids occur?
Fatty acids are major components of the skin. They primarily come from two distinct sources: the sebaceous glands and the extracellular matrix secreted by keratinocytes. The former produce the sebum, which is composed of 15-30% fatty acids, one of the constituents of the hydrolipidic film. Fatty acids are also found in the stratum corneum, accounting for about 10-15%, along with other lipids (ceramides and cholesterol). The primary function of skin lipids is to form a protective barrier against water loss, inflammatory reactions, and the entry of microorganisms.
However, the sensitivity of fatty acids to oxidation can alter their properties and compromise the integrity of the skin barrier.
Indeed, unsaturated fatty acids, meaning those with one or more double bonds in their chemical structure, can undergo oxidation when they come into contact with reactive oxygen species. These are naturally generated in skin tissues by metabolism or due to exposure to UV rays from the sun or pollution. When this type of free radical, whose chemical structure has an unpaired electron, comes into contact with a fatty acid, it snatches a hydrogen atom from one of the carbons adjacent to a double bond. This action triggers the formation of a lipid radical, an unstable species that reacts very quickly with the oxygen in the air during a reaction known as: lipid peroxidation.
This new free radical then seeks to stabilise itself by capturing an electron from a neighbouring fatty acid, generating a new radical. This mechanism creates a chain reaction where fatty acids are progressively oxidised one after the other. This process stops due to the intervention of antioxidants, such as vitamin E or glutathione, which neutralise the free radicals, or when the skin's endogenous antioxidant defences are exhausted, leading to the accumulation of lipid peroxides and oxidised by-products.
Saturated fatty acid (A: stearic acid) and unsaturated fatty acid (alpha-linolenic acid).
Source: Dongdi LI's Thesis. Bioinformatics-based approaches to engineer the transmembrane Δ6 desaturase from Micromonas pusilla (2016).
Does the oxidation of fatty acids lead to skin dehydration?
The oxidation of fatty acids is a process that alters the lipid structure of the skin and, consequently, the effectiveness of its barrier function.
This alteration directly impacts the skin's water retention capacity. Normally, when intercellular lipids are well organised, the stratum corneum can effectively retain water in the skin tissues. However, this changes when the oxidation of fatty acids disrupts this organisation by fragmenting the lipids. For instance, linoleic acid, which is present in large quantities in the stratum corneum, limits transepidermal water loss (TEWL) by binding to the skin's water molecules. When the levels of this fatty acid decrease, TEWL and skin dehydration increase. Studies have also shown that the absence of ELOVL4, an enzyme involved in the elongation of very long fatty acids, weakens the skin barrier by reducing the amount of lipids in the stratum corneum, which exacerbates skin dehydration and can even lead to the emergence of dermatoses, such as eczema, characterised by an alteration of the skin's barrier function and significant water loss.
A recent double-blind controlled study involving 32 children with atopic dermatitis has highlighted the potential benefits of linolenic acid, a fatty acid, in restoring the skin barrier. For this purpose, borage oil enriched with linolenic acid was incorporated into cotton shirts. The patients in the "linolenic acid" group wore these shirts daily, while those in the placebo group received pure cotton shirts. Two weeks later, erythema, itching, and also TEWL had significantly decreased. These results suggest that linolenic acid could potentially play a role in improving the skin barrier function and that its oxidation could conversely lead to skin dehydration.
Finally, the oxidation products of fatty acids can be the source of an inflammatory reaction that exacerbates the deterioration of the skin barrier. Indeed, an increased production of pro-inflammatory cytokines and mediators, such as prostaglandins, amplifies the damage and creates a vicious cycle: the skin becomes more permeable, water loss accelerates, and skin dryness sets in.
To combat the oxidation of fatty acids and thus dehydration, it is beneficial to incorporate antioxidants into your skincare routine.
Sources
JACOBS B. & al. Measurement of peroxisomal fatty acid beta-oxidation in cultured human skin fibroblasts. Journal of inherited metabolism disease (1995).
JUDDE A. Prévention de l’oxydation des acides gras dans un produit cosmétique : mécanismes, conséquences, moyens de mesure, quels antioxydants pour quelles applications ? Oilseeds and fats, Crops and Lipids (2004).
BONTÉ F. & al. Skin hydration: a review on its molecular mechanisms. Journal of Cosmetic Dermatology (2007).
KANEHARA S. & al. Clinical effects of undershirts coated with borage oil on children with atopic dermatitis: a double-blind, placebo-controlled clinical trial. The Journal of dermatology (2007).
PICARDO M. & al. Lipid mediators in skin inflammation: updates and current views. Mediators of Inflammation (2010).
Thèse de Dongdi LI. Bioinformatics-based approaches to engineer the transmembrane Δ6 desaturase from Micromonas pusilla (2016).
SONG L. & al. A review of fatty acids influencing skin condition. Journal of Cosmetic Dermatology (2020).
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