Clinical and Translational Allergy 2017, 7(Supple 4):O01
Background: Methylisothiazolinone (MI) is used as a preservative in occupational, domestic products and, since 2005, in cosmetics. It is a part of the preparation of methylchloroisothiazolinone (MCI)/MI and only in the last years started to be tested as a single allergen in the baseline series. According to recent studies, the sensitization rate for MI varies between 1 and 6%, with a marked increase, particularly in the late years. Objectives: To describe patients sensitized to MI and MCI/MI and investigate its prevalence among patch tested patients
Methods: Cross-sectional retrospective study, including all patients who performed, from 2011 to 2016, the European and Portuguese baseline patch test series, in a Dermatology department of a tertiary hospital. Those positive to MI and/or MCI/MI, were selected.
Results: During the study period, 1768 patients (70% women), performed the baseline series; 972 (55%) tested positive according to the International Contact Dermatitis Research Group’s scoring system. Of these, 114 individuals (11.7%) presented positivity to MI and/or MCI/MI; 81 (71%) were women; mean age (minimum-maximum) of 44.3 (8–86) years; 33.3% had previous history of atopic comorbidities. Hands either isolated or associated with other body parts were the most frequent symptomatic location (54 cases, 47.4%) followed by generalized dermatitis (33 cases, 29%). Further comparison of MI sensitization revealed no significant differences with respect to gender (p = 0.267), age (p = 0.616), or the presence of allergic comorbidities (p = 0.536). In 2011, only one patient (0.3%) tested positive to MCI/MI and after June 2012 patients (1.1%) were positive to MI. After 2012 we observed a significant increase in MI sensitization, which rose from 5.7% in 2013 to 6.3, 11.9 and 12.2% in 2014, 2015 and 2016, respectively.
Conclusions: We observed that, between 2012 and 2016, sensitization to methylisothiazolinone has grown more than tenfold. These data provide further evidence of the increasing MI sensibilization epidemic over the last years, as reported in several European countries, and reinforces the need to determine safer use concentrations in the products, namely, rinse-of cosmetics.