A multicenter study was performed in 9 Italian centers by members of the GIRDCA, to evaluate the frequency and source of contact sensitization in a group of 302 hairdressers with dermatitis. Occupational habits and use of preventive measures were specifically investigated both in these 302 hairdressers and in a further group of 240 hairdressers who answered a questionnaire. The results showed the presence of an occupationally relevant sensitization in 60.9% of the 302 hairdressers. This proportion included 52 hairdressers who had negative patch tests to the hairdressers' series but showed positive reactions to other allergens, such as nickel, rubber additives, preservatives and fragrances, which were judged relevant to their occupation. Among hair dyes, PPD caused 73 reactions (24.2%), PAP 32 reactions (10.6%), ONPPD 24 reactions (7.9%), and PTD 40 reactions (13.2%). A low incidence of sensitization was detected in our hairdressers to resorcinol and pyrogallol (1.3% for each substance). Among permanent wave allergens, positive reactions to GMTG were found in 11.3% of patients, while ATG gave a lower rate of positive reactions (5.0%). Allergic contact dermatitis due to APS was also relatively common (11.3%). 4 hairdressers in this study gave a positive reaction 30 min after a provocative test with latex gloves, patch testing to the rubber series being negative. Enquiry regarding preventive measures revealed that the majority of hairdressers use gloves when doing hair dyeing, but rarely use them for washing dyed hair or for doing permanent waving. The infrequent use of preventive measures by Italian hairdressers was confirmed by the results of the questionnaire, and possibly explains the high frequency of skin problems (12.5%) in the hairdressing population that was specifically interviewed.