Methylisothiazolinone allergic contact dermatitis: Assessment of relapses in 139 patients after avoidance advice.

Background: Methylisothiazolinone (MI) is a preservative that is responsible for an epidemic of allergic contact dermatitis (ACD). Few studies have been published on the prognosis of patients with MI-induced ACD.

Objectives: To evaluate relapses of MI-induced ACD and difficulties in avoiding MI in patients who had received avoidance advice.

Methods: A retrospective study of patients with MI-induced ACD diagnosed in two specialized dermato-allergology units between 2010 and 2015 was performed. The median follow-up was 3 years.

Results: Relapses were observed in 64% of 139 included patients, and were severe in 18%. Rinse-off cosmetics were responsible for the largest proportion of relapses (27%). The median time to relapse was 5 months. Sixty-nine per cent of relapses were on the hands, and 29% were on the face. Risk factors for relapsing were hand eczema and a personal history of atopy. The main difficulties encountered in the avoidance strategy were hidden sources of MI, the lack of labelling on industrial products, the complexity of cosmetic labelling, and remembering the name of the allergen.

Conclusion: MI-induced ACD has a poor prognosis. Its high rate of relapse is mainly attributable to the difficulties of avoidance. Management needs to be improved. Specialized follow-up in the year following diagnosis is essential to educate patients.