More than just methylisothiazolinone: Retrospective analysis of patients with isothiazolinone allergy in North America, 2017-2020

• Published in: Journal of the American Academy of Dermatology Vol. 90; no. 2; pp. 319 - 327
• Main Authors: Reeder, Margo J., Zhang, Donglin, Aravamuthan, Srikanth R., Warshaw, Erin M., DeKoven, Joel G., Silverberg, Jonathan I., Adler, Brandon L., Atwater, Amber R., Taylor, James S., Houle, Marie-Claude, Belsito, Donald V., Yu, Jiade, Botto, Nina, Mowad, Christen M., Dunnick, Cory A., DeLeo, Vincent A., Pratt, Melanie D.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-02-2024
• Subjects: Allergens - adverse effects; allergic contact dermatitis; Cross-Sectional Studies; Dermatitis, Allergic Contact - diagnosis; Dermatitis, Allergic Contact - epidemiology; Dermatitis, Allergic Contact - etiology; Dermatitis, Occupational - diagnosis; Dermatitis, Occupational - epidemiology; Dermatitis, Occupational - etiology; Humans; methylisothiazolinone; North America; patch testing; Patch Tests - adverse effects; Petrolatum; Preservatives, Pharmaceutical - adverse effects; Retrospective Studies; Thiazoles; North America; ACD; MCI; allergic contact dermatitis; methylisothiazolinone; NACDG; OIT; patch testing; BIT; MI; PCP
• ISSN: 0190-9622; 1097-6787
• DOI: 10.1016/j.jaad.2023.10.032

Isothiazolinones are a common cause of allergic contact dermatitis.
To examine the prevalence of positive patch test reactions to isothiazolinones from 2017-2020 and characterize isothiazolinone-allergic (Is+) patients compared with isothiazolinone nonallergic (Is–) patients.
Retrospective cross-sectional analysis of 9028 patients patch tested to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) 0.02% aqueous, MI 0.2% aqueous, benzisothiazolinone (BIT) 0.1% petrolatum, and/or octylisothiazolinone (OIT) 0.025% petrolatum. Prevalence, reaction strength, concurrent reactions, clinical relevance, and source of allergens were tabulated.
In total, 21.9% (1976/9028) of patients had a positive reaction to 1 or more isothiazolinones. Positivity to MI was 14.4% (1296/9012), MCI/MI was 10.0% (903/9017), BIT was 8.6% (777/9018), and OIT was 05% (49/9028). Compared with Is–, Is+ patients were more likely to have occupational skin disease (16.5% vs 10.3%, P <.001), primary hand dermatitis (30.2% vs 19.7%, P <.001), and be >40 years (73.1% vs 61.9%, P <.001). Positive patch test reactions to >1 isothiazolinone occurred in 44.1% (871/1976) of Is+ patients. Testing solely to MCI/MI would miss 47.3% (611/1292) of MI and 60.1% (466/776) of BIT allergic reactions.
Retrospective cross-sectional study design and lack of follow-up data.
Sensitization to isothiazolinones is high and concurrent sensitization to multiple isothiazolinone allergens is common.