Arachidic Acid

Arachidic acid is a long-chain saturated fatty acid used in cosmetics primarily as an emollient/structuring agent at low percentages, and fatty acids of this type are generally well-tolerated on skin. It is not a low‑pH active and is not commonly associated with significant irritation in standard use, though any lipid component can occasionally provoke mild stinging or follicular/irritant reactions in highly reactive or barrier-impaired users. Given its typical low concentration and low intrinsic reactivity, I rate it as very gentle with a small but nonzero risk in severely sensitive populations. Safety Notes: Arachidic acid (C20:0) is most often present as a minor fatty-acid component of plant butters/waxes or as a co-structurant in emulsions, so in many mainstream leave-on creams/lotions it appears at trace-to-low levels (often around 0.001–0.1%) when added as part of a fatty-acid blend rather than as a headline active. Higher consumer-available levels occur in heavy body butters, balms, cleansing creams, and anhydrous stick products where long-chain fatty acids are used to build structure and slip; in those formats arachidic acid can be used at a few percent, with observed upper-end OTC formulations around ~5% when deliberately added for thickening/consistency. There are no specific EU/FDA maximum limits for arachidic acid as a cosmetic ingredient, so the practical ceiling is driven by texture, crystallization/whitening risk, and overall fatty-phase design rather than regulation.