Allergic contact dermatitis from propylene glycol: A case series from Australia

Background: Propylene glycol (PG) is used in a variety of cosmetics, food and pharmaceuticals. PG is a known sensitizer but also irritating when patch tested (PT).Objectives: The aims were to investigate the frequency of contact sensitization to PG and to identify cases of allergic contact dermatitis (ACD).Methods: A retrospective study was performed on patients PT at the Skin Health Institute (SHI), Victoria, Australia to PG 5% pet. and PG 10% aq. between 1 January 2005 and 31 December 2020.Results: In all, 6761 patients were PT to PG and 21 (0.31%) reacted. Of those 21 individuals, 9 (42.9%) had a relevant reaction. 75% of relevant positive reactions were in patients PT to PG 10% aq. The most common source of PG exposure was topical medicaments (77.8% of relevant reactions) and moisturizers, with the largest group being topical corticosteroids.Conclusion: Contact sensitization to PG in the patch test population remains uncommon, although it is possible that testing with concentrations of 5%-10% PG did not identify all reactions. Topical corticosteroids were the most important cause. Patients with suspected contact dermatitis to topical corticosteroids should be PT to PG.