Glycerin
Also known as Glycerol, Glycerine, 1,2,3-Propanetriol, Propane-1,2,3-triol, Trihydroxypropane
“CIR Expert Panel says: safe as used in cosmetics.”
Glycerin (glycerol; 1,2,3-propanetriol; CAS 56-81-5) is a simple polyol used as a humectant, skin conditioning agent, and skin protectant. It is one of the most widely used cosmetic ingredients — the CIR 2014 final report notes it was the third most frequently reported ingredient in the US VCRP database (after water and fragrance), with 15,654 reported product uses including 7,756 skin care products, 862 products for use near the eye, and 125 baby products. The Cosmetic Ingredient Review Expert Panel concluded glycerin is 'safe as a cosmetic ingredient in the practices of use and concentration described' (Becker et al., Int J Toxicol 2019, PMID 31840548). Animal and human data cited in the assessment show glycerin is not dermally irritating in rabbits at concentrations up to 100%, not irritating at 50% in human dermatitis patients, and only a mild irritant at 100% in guinea pigs. Mechanistically, Fluhr, Darlenski & Surber (Br J Dermatol 2008, PMID 18510666) describe glycerol as a multifunctional skin agent that enhances stratum corneum hydration, strengthens epidermal barrier function, supports skin elasticity via aquaporin-3 transport, and accelerates wound healing. A 20% glycerin cream in Lodén & Wessman (Int J Cosmet Sci 2001, PMID 18498456) significantly increased skin hydration after 10 days of daily application without affecting transepidermal water loss or SLS-induced irritant response. Glycerin is also FDA Generally Recognized As Safe (GRAS) for food use.
Humectant and skin conditioning agent — draws and retains moisture in the stratum corneum (Fluhr 2008; CIR 2014)
20% glycerin cream significantly increased skin hydration after 10 days of daily use without affecting TEWL or SLS-induced irritant response (Loden & Wessman 2001)
Strengthens epidermal barrier function and supports endogenous aquaporin-3-mediated water transport in the skin (Fluhr 2008)
Accelerates wound healing; beneficial for atopic dermatitis and winter xerosis (Fluhr 2008)
FDA Generally Recognized As Safe (GRAS) for food use; long history of safe cosmetic use across 15,654 reported product applications in the US VCRP database (CIR 2014)
- · Mild dermal irritation observed at undiluted (100%) concentration in guinea pigs in the CIR 2014 safety assessment
Theoretical risk at very high topical concentrations in low-humidity environments that glycerin may draw moisture from deeper skin layers rather than from the air — raised in consumer-education literature, not substantiated as a clinical safety issue by the CIR panel or the Fluhr 2008 review
CIR Quick Reference Table (12/2017, revised 07/2018) - Glycerin row: Finding 'S' (Safe), Citation 'Final report 12/2014 available from CIR'
“Glycerin | S | [no detail column entry] | Final report 12/2014 available from CIR”— QRT-122017revised072018.pdf, p. 51