Butylene Glycol

Evidence by route

About this ingredient

Butylene Glycol (1,3-Butanediol) is a synthetic four-carbon glycol, one of the most widespread solvents and humectants in modern cosmetics. Mechanism. On skin it has three roles. Humectant – binds water and holds it in the stratum corneum (weaker than glycerin but non-sticky). Solvent – improves solubility of poorly water-miscible actives (e.g. niacinamide, retinol, azelaic acid). Penetration enhancer – briefly increases stratum corneum permeability, helping actives penetrate. Where applied. Serums, toners, creams, shampoos, makeup primers, micellar waters. Concentration 1–20%. In Spain found in nearly every La Roche-Posay, Avène, ISDIN, Sesderma, Bioderma formula. One of the most common 21st-century cosmetic ingredients. Safety. CIR confirmed safety in 2017. Hypoallergenic, non-comedogenic, non-irritating (unlike propylene glycol, which some patients react to). Topical systemic absorption is low. Contact allergies are isolated – less than 0.1% positive patch tests. Pregnancy and lactation – safe. Used without restriction. Controversies. 'Natural cosmetics' marketing sometimes labels it synthetic and undesirable. At the SCCS, CIR, and AEMPS level the position is stable: safe at cosmetic concentrations. A good choice for patients intolerant to propylene glycol. Functional role. A universal formula aid. No distinct standalone activity as an active – works as humectant, solvent, and penetration enhancer.

Tolerability and safety

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