Prevalence and factors associated with sensitivity to methylisothiazolinone in individuals with suspected allergic contact dermatitis: A cross-sectional study.

Objectives: To evaluate the prevalence of methylisothiazolinone sensitivity and associated factors in individuals with suspected allergic contact dermatitis.

Methods: Cross-sectional study based on patch tests, including methylisothiazolinone 0.2%, in 286 participants with suspected allergic contact dermatitis, in Brasília/DF, Brazil, between March/2020 and March/2022.

Results: 13.6% of participants were diagnosed with allergic contact dermatitis and sensitive to MI. The mean age was 43.7 years, and the majority were women (71,8%). The average duration of the disease was 60 months. The most common location was hands (76.9%) and upper limbs (33.3%). In 97.4%, allergy to methylisothiazolinone was considered of current relevance. In the multivariate model, being domestic/household increased the chance of presenting sensitivity to MI by 4.2 (95% CI= 1.36 - 13.5). Presenting lesions in several places of the body was also significantly associated (OR=2.84; CI 95%=1.17 - 6.86) to be sensitive to the test substance.

Conclusion: The findings confirm the epidemic of allergy to methylisothiazolinone. They reinforce the need for the inclusion of this isolated substance in the Brazilian baseline series. We emphasize the need for regulations on the use of methylisothiazolinone in industrial products and household detergents, as is done for cosmetics. Studies in other centers are needed to confirm these results.