Propylene glycol: irritation or sensitization?

Irritation and sensitization patch test studies were conducted using propylene glycol in an attempt to ascertain the nature of the cutaneous response to this commonly employed topical excipient. A total of 10 and 203 subjects completed standard irritation and sensitization protocols, respectively. A provocative use test was conducted on subjects reacting to propylene glycol. Results indicate that propylene glycol is at least a minimal irritant. Fleeting evidence suggestive of sensitization was observed during patch testing but was not substantiated upon provocative use testing. Interpretation of these results is presented; however, the nature of the cutaneous response to propylene glycol remains obscure.