Evolution of methylisothiazolinone sensitization: A Belgian multicentric study from 2014 to 2019

Area of Science:

• Dermatology
• Toxicology
• Epidemiology

Background:

• An epidemic of allergic contact dermatitis to methylisothiazolinone (MI) occurred in Europe during the 2010s.
• Regulatory actions in 2017 and 2018 restricted MI use in cosmetics.
• The study addresses the impact of these regulations on MI sensitization rates.

Purpose of the Study:

• To determine the sensitization rate to methylisothiazolinone (MI) in Belgium from 2014 to 2019.
• To investigate co-sensitization patterns with octylisothiazolinone (OIT) and benzisothiazolinone (BIT) in MI-allergic patients.
• To evaluate the effectiveness of regulatory measures on MI allergy prevalence.

Main Methods:

• Retrospective analysis of patch test data from five Belgian hospitals.
• Inclusion of patients tested for MI, OIT, and BIT.
• Data collected between January 2014 and December 2019.

Main Results:

• A total of 5.58% of patients (560/10,029) showed positive patch test reactions to MI.
• The MI sensitization rate declined from 7.9% in 2014 to 3.1% in 2019.
• Common sources included rinse-off cosmetics, paints, and detergents; frequent co-sensitization to OIT and BIT was observed.

Conclusions:

• Contact allergy to MI in Belgium has decreased to pre-epidemic levels, indicating regulatory success.
• Leave-on cosmetics are no longer a significant source of MI sensitization in Europe.
• Paints and detergents remain problematic, and the high rate of BIT co-sensitization warrants further research.