PROPYLENE-GLYCOL DERMATITIS - REEVALUATION OF AN OLD PROBLEM

Evaluation of dermatitis associated with propylene glycol application or ingestion remains a challenge. The research dealing with skin react ions to propylene glycol is revisited and new aspects for future resea rch are outlined. Based on literature review and our own observations, we propose classifying skin reactions to propylene glycol into 4 mech anisms: (a) irritant contact dermatitis, (b) allergic contact dermatit is, (c) non-immunologic contact urticaria, and (d) subjective or senso ry irritation. This concept allows a partial explanation of effects ob served by different authors. Despite attempts to define objective crit eria, biologically, histopathologically, or clinically, the distinctio n between irritant and allergic reactions remains unclear. Furthermore , the irritation threshold of propylene glycol, and likewise the optim al standard concentration in patch tests, is sub judice. Future studie s on propylene glycol dermatitis should include repeated patch tests w ith serial dose dilutions, repeated open application tests/provocative use tests, oral challenge tests, and biopsies for a more complete eva luation of mechanisms and clinical significance.