Imidazoles and nitroimidazoles belong to a group of heterocyclic and nitroheterocyclic compounds that are mainly used as broad-spectrum anti-infectious agents. 1 Adverse effects are relatively rare 2 ; in particular, allergic contact dermatitis (ACD) is comparatively rare, considering the high prescription rates. 3 In a few cases of ACD caused by metronidazole 4,5 and clotrimazole, 6 , sensitivity to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) coexisted.
MATERIALS AND METHODS
BetweenJune 2015 and December 2016, 149 patients (35 men and 114 women; mean age 40.0 years) recently diagnosed as being sensitized to MCI/MI (0.02% aq.), mainly because of the use of cosmetics, were patch tested with phenethyl imidazoles (econazole nitrate, fenticonazole nitrate, isoconazole nitrate, ketoconazole, miconazole nitrate, sertaconazole nitrate, and tioconazole) and phenmethyl imidazoles (bifonazole nitrate and clotrimazole), all at 2% pet., 7 as well as with nitroimidazoles, both antiprotozoals (metronidazole and tinidazole) and antihelmintics (albendazole and mebendazole), all at 5% pet. (FIRMA, Florence, Italy). We also tested MCI MI at the same concentrations as in the commercial blend (0.015% aq. and 0.005% aq., respectively); MI 0.2% aq. was also tested to avoid false-negative reactions. 8 Patch tests were performed in accordance with ESCD recommendations, with Haye's Test Chambers (Haye's Service, Alphen aan den Rijn, The Netherlands) on Soffix tape (Artsana, Grandate, Italy). Micropipettes were used for aqueous allergens, and haptens were simultaneously occluded for 2 days. Readings were performed on day (D) 2 and D4. A computerized conformational analysis (TRYDENT V1.0.0 software; Molecular Modeling for Medicinal Chemists, Wavefunction, Irvine,California) was carried out to study the spatial electron cloud geometries of MCI, MI and the imidazoles/nitroimidazoles that gave positive reactions in patch tests. 9