Contact allergy to isothiazolinones epidemic: Current situation.

BACKGROUND: Since 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. OBJECTIVES: To analyze the incidence of isothiazolinone-related ACD in our area in the last decade. METHODS: A 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. RESULTS: A 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. CONCLUSIONS: As 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.

European photopatch test baseline series: A 3-year experience.

BACKGROUND: In 2012, a consensus was reached regarding a baseline photopatch test series on the basis of the results of a European multicentre study. OBJECTIVES: To describe experience with the European photopatch test series. METHODS: A retrospective analysis of 116 patients tested with the European photopatch test series between 2014 and 2016 was performed. RESULTS: Fifty-five positive photopatch test reactions in 25 subjects were recorded, most commonly caused by the topical non-steroidal anti-inflammatory drugs ketoprofen, dexketoprofen, and etofenomate. Organic ultraviolet (UV) absorbers constituted the second main category of agents eliciting positive photopatch test reactions. Among UV absorbers, benozophenone-3 and octocrylene were the most frequent photoallergens. UV absorbers that have been introduced more recently rarely elicited positive photopatch test reactions. Positive patch test reactions were less commonly observed than positive photopatch test reactions, namely, 21 reactions in 14 patients. CONCLUSIONS: We present the largest clinical experience with the European photopatch test baseline series hitherto reported. The results are similar to those underlying the above consensus process, reaffirming the usefulness of this series.