We report a case of contact dermatitis caused by both efinaconazole, a topical triazole antifungal drug, and luliconazole, a topical imidazole antifungal drug. Positive patch test reactions were observed with efinaconazole and luliconazole. A patch test with lanoconazole also elicited a positive reaction. We hypothesized that structural similarity between luliconazole and lanoconazole led to cross-reaction, and that the dithiolane ring common to both drugs or the structure of the vinyl imidazole with a dithiolane ring could be the antigenic determinant. Since efinaconazole and luliconazole have no common structures, patients could be sensitized to both drugs separately. The antigenic determinant of efinaconazole is unknown. However, the chemical formula of ravuconazole, an oral triazole antifungal drug, is similar to that of efinaconazole. Clinicians should carefully consider potential cross-reactivity between these drugs.
Keywords: contact dermatitis; cross-reaction; efinaconazole; luliconazole; triazole.