Hyaluronic Acid vs Propylene Glycol (Cosmetic): which is worse?

What is Hyaluronic Acid?

Hyaluronic acid (HA) is a naturally occurring polysaccharide (glycosaminoglycan) found abundantly in human skin, connective tissue, and eyes. It can hold up to 1,000 times its weight in water. In cosmetics, HA is typically produced via bacterial fermentation of Streptococcus equi.

What is Propylene Glycol (Cosmetic)?

Propylene glycol is a small synthetic organic compound (diol) used in cosmetics as a humectant, solvent, and skin-conditioning agent. It is produced from propylene oxide (petroleum) but also from bio-based sources.

Documented risks

Hyaluronic Acid: Hyaluronic acid is among the safest cosmetic active ingredients available. As an endogenous molecule in the human body, it is exceptionally biocompatible and essentially non-allergenic in topical form. The CIR has confirmed its cosmetic safety. No carcinogenicity, endocrine disruption, or significant adverse effects are documented. Rare reports of pore congestion exist with certain high-MW HA in oily skin, but these are minimal.

Propylene Glycol (Cosmetic): Propylene glycol is safe at typical cosmetic use concentrations (1–15%). The CIR and EU SCCS have both reviewed and affirmed its safety. It can cause contact sensitization and irritant reactions in some individuals, particularly at concentrations above 5% in leave-on products; those with sensitive or compromised skin may react. It is rapidly metabolized if absorbed and is not bioaccumulative. There is no evidence of carcinogenicity or endocrine disruption at cosmetic use levels. Note: this entry covers topical cosmetic use; ingested large doses (antifreeze context) are toxic, which is a separate matter.