, a trend that is likely driven by regulatory differences, a retrospective cohort study suggests.
“Between 2009 to 2018, the global burden of isothiazolinone allergy showed divergent trends between North American and European countries,” lead study author Margo J. Reeder, MD, of the University of Wisconsin in Madison and her colleagues write. The study was published online in JAMA Dermatology.
Isothiazolinone contact allergy peaked in Europe in 2013-2014 before gradually decreasing, they found. The prevalence of isothiazolinone allergy steadily increased in North America during the study period. “Earlier and more stringent regulation of MI [methylisothiazolinone] in Europe is associated with these divergent trends,” they write.
Common ingredients worldwide
Isothiazolinone preservatives, which are added to personal and industrial products, cause allergic contact dermatitis worldwide, the authors write. The preservatives are found in a wide range of leave-on and rinse-off water-based personal care products, such as shampoo and other hair products, dishwashing liquid, face cream, body lotion, shower gel, liquid soap, and wet wipes, as well as in water-based paint.
A mixture of methylchloroisothiazolinone (MCI) and MI has been used to prevent microbial growth in products since the 1980s. In 2005, U.S. and European regulators approved MI alone at higher concentrations as a preservative in personal care products. Coupled with consumer concerns about other preservatives, such as parabens (a rare allergen), use of MI in personal care products increased, the authors write.
Subsequently, researchers reported a global increase in the prevalence of contact allergy to isothiazolinones, the authors write. Regulatory restrictions on MI in personal care products were implemented in 2013 in Europe and in 2015 in Canada but not in the United States.
Patch test data reveal latest trends
To compare prevalence trends of allergic contact allergy to MI and sensitization to the MCI/MI mixture in North America and in Europe, Dr. Reeder and her colleagues compared the prevalence of positive patch test reactions to MCI/MI and to MI alone in North America and in Europe between 2009 and 2018.
They analyzed data from the North American Contact Dermatitis Group (NACDG), the European Surveillance System on Contact Allergies (ESSCA), and the Information Network of Departments of Dermatology (IVDK) in 2-year intervals. The data came from patients who had been patch tested at referral patch test clinics in North America and Europe.
Over the decade, the study sites conducted patch testing for 226,161 patients for MCI/MI and 118,779 for MI. Most data came from Europe. The researchers found the following:
- In Europe, isothiazolinone allergy peaked in 2013 and 2014; MCI/MI positivity reached 7.6% (ESSCA) and 5.4% (IVDK) before decreasing to 4.4% (ESSCA) and 3.2% (IVDK) in 2017-2018.
- In North America, MCI/MI positivity rose steadily from 2.5% in 2009-2010 to 10.8% in 2017-2018.
- In Europe, there were 5.5% (ESSCA) and 3.4% (IVDK) positive reactions to MI, compared with 15% (NACDG) in North America in 2017-2018.