Appropriate Testing of Isothiazolinones in Children

Area of Science:

• Dermatology
• Allergology
• Pediatrics

Background:

• Isothiazolinones, specifically methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI), are common causes of allergic contact dermatitis (ACD) in children.
• Methylisothiazolinone (MI) associated ACD is frequently underreported in scientific literature.

Purpose of the Study:

• To determine the prevalence of positive patch tests (PPTs) for MCI/MI and MI alone in U.S. pediatric cases.
• To evaluate the diagnostic yield of different patch testing strategies for MI sensitization.

Main Methods:

• Utilized a database of provider-reported U.S. pediatric patch test cases from across all 50 states.
• Analyzed over 1100 logged cases for positive patch tests to MCI/MI combination and MI alone.

Main Results:

• Identified 96 cases with positive patch tests within one year; 37 reacted to MCI/MI (MI alone negative/not tested), and 39 reacted to MI alone.
• Comprehensive patch testing identified 51% more MI allergies than testing with MCI/MI alone.
• Only 3% of MI-alone sensitizations were detected with standard testing; 97% required comprehensive testing.

Conclusions:

• Accurate assessment of isothiazolinone sensitization requires specific testing for MI, in addition to MCI/MI.
• Patch testing for MI alone is recommended for children with persistent or recalcitrant dermatitis to identify underlying sensitization.