Contact Allergy and Allergic Contact Dermatitis From Propylene Glycol and Related Glycols: Cosmetic Skin Sensitisers After All?

BACKGROUND

Propylene glycol (PG) is widely used in cosmetic and pharmaceutical products, yet data on the prevalence of contact allergy to PG and related glycols, and their potential cross-reactivity, remain limited.

OBJECTIVES

To determine the prevalence of glycol contact allergy, describe clinical characteristics and assess potential cross-reactivity.

METHODS

We retrospectively analysed 1979 patients patch tested at Antwerp University Hospital between January 2021 and December 2024 who were tested with at least one glycol.

RESULTS

Fifty-five patients (2.79%) were allergic to PG. Detection rates for PG increased with concentration: 5% petrolatum (1.06%), 10% aqueous (0%), 20% aqueous (0.66%), 30% aqueous (2.19%) and 100% (7.82%, selectively tested). Pentylene glycol allergy was found in 6.74% (6/89) and caprylyl glycol in 0.77% (5% petrolatum) and 0.12% (1% petrolatum). Concomitant reactions to PG occurred in 4/6 pentylene glycol-allergic and 2/9 caprylyl glycol-allergic patients. PG-allergic patients were predominantly female (63.6%), with dermatitis mainly affecting the face and hands. Cosmetics (67.3%) were the most common exposure source, followed by topical pharmaceuticals (41.8%).

CONCLUSIONS

Thirty percent aqueous PG appears more suitable for screening than lower concentrations, and 100% PG may improve detection in selected cases. Cross-reactivity seems limited and is most evident among structurally similar short-chain glycols.