Linoleic Acid
Also known as Linoleic acid, cis,cis-9,12-Octadecadienoic acid, C18:2 fatty acid, Omega-6 fatty acid, 9,12-Octadecadienoic acid
“CIR Expert Panel says: safe as used in cosmetics.”
Linoleic Acid (cis,cis-9,12-octadecadienoic acid; CAS 60-33-3; C18H32O2) is a polyunsaturated C18 omega-6 essential fatty acid abundant in plant oils (sunflower, safflower, corn, soybean) and a natural component of human sebum and stratum corneum ceramides. The CIR Expert Panel assessed it as part of the 2019 'Safety Assessment of Fatty Acids and Fatty Acid Salts' (Int J Toxicol 38(Suppl 1):5-102, 2019) and concluded it is safe when formulated to be non-irritating and non-sensitizing — an SQ finding reflecting the Panel's concern that polyunsaturated fatty acids can undergo oxidation during formulation and storage to produce oxidation products that may act as dermal sensitizers. Sensitization evidence included a positive DPRA and a weak response in the LLNA:DAE assay at 25%. Genotoxicity studies (Ames test) were negative. PubMed literature supports its role as an essential component of lamellar body lipids and skin barrier ceramide synthesis, with deficiency linked to impaired barrier function and ichthyosis.
Essential omega-6 fatty acid and natural component of human sebum, stratum corneum ceramides, and lamellar body lipids — plays a critical role in skin barrier function
CIR Expert Panel concluded safe in cosmetics in the present practices of use and concentration when formulated to be non-irritating and non-sensitizing (Int J Toxicol 38(Suppl 1):5-102, 2019)
Used as emollient, hair conditioning agent, skin-conditioning agent, fragrance ingredient, and surfactant-cleansing agent in 681 cosmetic product uses (up to 21.8% rinse-off, up to 3.4% leave-on per CIR assessment)
Deficiency in linoleic acid impairs lamellar body secretion and stratum corneum barrier integrity; topical application can restore barrier function in essential fatty acid deficiency models
Negative genotoxicity profile: non-mutagenic in Ames test (Ref 63 of CIR 2019 report)
- · Polyunsaturated fatty acid subject to oxidation during formulation and storage; oxidation products may be dermal sensitizers — the basis for the CIR SQ (qualified safety) finding
- · Weak skin sensitizer signal: positive DPRA assay and weak LLNA:DAE response at 25% concentration reported in the 2019 CIR assessment
- · CIR recommends formulation be evaluated for non-irritancy and non-sensitization, potentially via quantitative risk assessment (QRA)
CIR Quick Reference Table Update October 2024 — Linoleic Acid row: Finding=SQ, Conclusion='...safe in the present practices of use and co…
“Linoleic Acid | SQ | The CIR Expert Panel concluded that the following ingredients are safe in the present practices of use andconcentration described in the safety assessment when formulated to be non-irritating and non-sensitizing, which may be basedon a QRA...Linoleic Acid... | Final Report 04/2019 Available from CIR”— QRT-Update-100824_0.pdf, p. 97