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The following is a summary of “More than just methylisothiazolinone: Retrospective analysis of patients with isothiazolinone allergy in North America, 2017-2020,” published in the February 2024 issue of Dermatology by Reeder, et al.
Isothiazolinones are a prevalent cause of allergic contact dermatitis, contributing significantly to skin sensitization. For a study, researchers sought to assess the prevalence of positive patch test reactions to isothiazolinones between 2017 and 2020 and to characterize patients allergic to isothiazolinones (Is+) compared to isothiazolinone nonallergic (Is–).
Conducting a retrospective cross-sectional analysis, the study included 9,028 patients subjected to patch testing with methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) 0.02% aqueous, MI 0.2% aqueous, benzisothiazolinone (BIT) 0.1% petrolatum, and/or octylisothiazolinone (OIT) 0.025% petrolatum. Parameters such as prevalence, reaction strength, concurrent reactions, clinical relevance, and allergen source were recorded.
Of the total, 21.9% (1,976/9,028) exhibited a positive reaction to one or more isothiazolinones. Positivity rates were as follows: MI 14.4%, MCI/MI 10.0%, BIT 8.6%, and OIT 0.5%. Is+ patients, in comparison to, Is–, showed higher tendencies for occupational skin disease (16.5% vs 10.3%, P < .001), primary hand dermatitis (30.2% vs 19.7%, P < .001), and age over 40 years (73.1% vs 61.9%, P < .001). Concurrent sensitization to multiple isothiazolinone allergens occurred in 44.1% (871/1,976) of Is+ patients. Sole testing for MCI/MI would overlook 47.3% of MI and 60.1% of BIT allergic reactions. The study’s retrospective cross-sectional design and lack of follow-up data could impact comprehensive insights.
Sensitization to isothiazolinones is prevalent, often involving concurrent sensitization to multiple isothiazolinone allergens. It emphasized the need for comprehensive testing strategies to diagnose and manage allergic contact dermatitis related to isothiazolinones.
Reference: jaad.org/article/S0190-9622(23)03035-9/fulltext
