AbstractBackgroundSince 2009, an increasing number of published cases of allergic contact dermatitis (ACD) from isothiazolinones in Europe was observed, amounting to an epidemic. However, only few studies have assessed the current situation after changes in European regulation.ObjectivesTo analyze the incidence of isothiazolinone‐related ACD in our area in the last decade.MethodsA retrospective study analyzed all patients patch tested in the allergy unit in a tertiary hospital in Spain between January 2010 and June 2019. Positive patch‐test reactions to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) and/or MI alone were recorded.ResultsA total of 243 patients (9.55%) with positive patch‐test reactions to MCI/MI and/or MI alone among 2544 consecutively patch‐tested patients were recorded. An initial increase in the prevalence of MCI/MI allergy was observed, from 4.5% in 2010 reaching a peak in 2015, which was followed by a significant decrease until July 2019 with 3.1% prevalence in 2019.ConclusionsAs shown in our data, regulatory interventions have resulted in a dramatic decrease in the prevalence of MCI and MI ACD, reaching a pre‐epidemic level of 3.1% in 2019.