Methylisothiazolinone contact allergy--growing epidemic

Area of Science:

• Dermatology
• Allergology
• Cosmetic Science

Background:

• Rising prevalence of contact allergy to isothiazolinone preservatives, specifically methylchloroisothiazolinone (MCI) with methylisothiazolinone (MI), and MI alone.
• Increased incidence observed in recent years necessitates further investigation.

Purpose of the Study:

• To determine the prevalence of contact allergy to MI, MCI/MI, and benzisothiazolinone (BIT) in patients undergoing patch testing.
• To assess the presence and use of MI in cosmetic products.

Main Methods:

• Retrospective analysis of patients patch tested for MI, MCI/MI, or BIT between 2010 and 2012.
• Registration of the MOAHLFA index and identification of relevant exposures in patients with isothiazolinone allergy.
• Market survey of cosmetic products to quantify MI content.

Main Results:

• Significant increase in MI and MCI/MI contact allergy prevalence from 2010 to 2012.
• MI-allergic patients frequently presented with occupational, hand, and facial dermatitis, and were over 40 years old.
• Cosmetics identified as the primary source of exposure for both MI and MCI/MI allergic patients; MI detected in 3.3% of Danish cosmetics.

Conclusions:

• The escalating rates of MI contact allergy are a significant concern.
• Immediate interventions are required to mitigate the increasing trend of MI-induced allergic contact dermatitis.