Linoleic Acid

Linoleic acid is an essential omega-6 fatty acid: the body cannot make it and must get it from food. It is the dominant fatty acid in Sunflower Seed Oil and makes up about 70% of Evening Primrose Oil (a 1 g Efamol capsule holds about 0.62 g linoleic acid; AAFP 2009). In the body it is converted to Gamma-Linolenic Acid (GLA), which is the basis of the old theory that eczema reflects poor conversion.

Linoleic Acid [part-of] Sunflower Seed Oil Linoleic Acid [part-of] Evening Primrose Oil Linoleic Acid [precedes] Gamma-Linolenic Acid

The linoleic:oleic ratio. Vaughn et al. (2018) reviewed plant oils for skin-barrier repair and argued that “differing ratios of essential fatty acids are major determinants” of benefit: oils with a higher linoleic-to-Oleic Acid ratio “have better barrier repair potential”, while oleic-rich oils may harm the barrier. Danby et al. (2013) supported this in adults: four weeks of sunflower seed oil preserved stratum corneum integrity and improved hydration, whereas Olive Oil damaged it. This is the main chemical reason sunflower oil is preferred over olive oil when parents want a plant oil for a toddler with Atopic Dermatitis. The evidence is mostly mechanistic and from adult or neonatal skin; no trial has tested linoleic-rich oil as an eczema treatment in toddlers.

Linoleic Acid [opposes] Oleic Acid Linoleic Acid [supports] Skin Barrier Dysfunction

Conflict: [Vaughn et al., Am J Clin Dermatol, 2018; Danby et al., Pediatr Dermatol, 2013] say high-linoleic oils such as sunflower support barrier repair. [Cooke et al., Acta Derm Venereol, 2016] found that in 115 healthy newborns, sunflower oil, like olive oil, led to significantly less improvement in lipid-lamellae structure than no oil. Unresolved — add to open_questions.

Safety and practical points. Linoleic acid is listed alongside urea, lactic acid and glycerol as an emollient ingredient reported to cause local irritation in some patients (Ho et al., Dermatol Ther). Oils on their own are not complete emollients: they contain no humectant and are less occlusive than Petrolatum. Many linoleic-rich oils are pressed from nuts or seeds, so avoid nut-derived oils on broken toddler skin.

Nut-based oils

Nut-derived oils applied to inflamed skin may sensitise a young child to that nut (see Peanut Oil Sensitisation). Prefer refined sunflower oil or a licensed emollient.

Linoleic Acid [relates] Peanut Oil Sensitisation

Connections

• Sunflower Seed Oil — dominant fatty acid, source: Vaughn 2018
• Oleic Acid — opposing fatty acid in the barrier ratio, source: Vaughn 2018
• Coconut Oil — low-unsaturated oil, ratio less relevant, source: Verallo-Rowell 2008
• Gamma-Linolenic Acid — converted from linoleic acid; basis of EPO theory, source: AAFP 2009
• Evening Primrose Oil — EPO is ~70% linoleic acid, source: AAFP 2009
• Shea Butter — minor fatty acid; claimed barrier support, source: Sivapiromrat 2021
• Olive Oil — low linoleic:oleic ratio; damaged adult barrier where sunflower did not, source: Danby 2013
• Peanut Oil Sensitisation — nut-oil hazard, source: vault note