Propylene Glycol (Cosmetic) vs Sodium PCA: which is worse?

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.

What is Sodium PCA?

Sodium PCA (sodium L-pyroglutamate) is the sodium salt of pyroglutamic acid, a naturally occurring component of the skin's Natural Moisturizing Factor (NMF). It is an exceptionally effective humectant with a higher water-binding capacity than glycerin.

Documented risks

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.

Sodium PCA: Sodium PCA is one of the safest and most skin-compatible humectants available. It is endogenous to healthy skin and has no known adverse effects. The CIR has confirmed its safety. It is non-irritating, non-sensitizing, non-comedogenic, and safe for all skin types.