Methylchloro-isothiazolinone revisited.

Area of Science:

• Dermatology
• Allergology
• Contact Dermatitis

Background:

• Preservatives represent a significant category of allergens frequently included in diagnostic testing series.
• Various preservative concentrations are present in common patch test kits, including the TRUE test, European series, and North American Series.
• Methylchloroisothiazolinone/methylisothiozolinone (MCI/MI) emerged as a notable preservative allergen in the 1980s.

Purpose of the Study:

• To evaluate the prevalence and significance of preservatives, particularly MCI/MI, within standard allergy testing protocols.
• To understand the trends in MCI/MI usage and reported contact allergies.
• To compare the sensitivity rates of MCI/MI with other common preservative allergens.

Main Methods:

• Analysis of preservative content in major patch testing series (TRUE test, European, North American).
• Review of literature and data regarding the introduction and use of MCI/MI.
• Examination of reported incidence rates of contact allergy to MCI/MI, referencing data from the North American Contact Dermatitis Group.

Main Results:

• The study highlights the substantial representation of preservatives within allergy testing.
• Methylchloroisothiazolinone/methylisothiozolinone (MCI/MI) has seen increased use since its introduction, leading to concerns about contact allergy.
• Reported sensitivity rates for MCI/MI are comparable to other preservatives, despite variations in allowable product levels and usage rates across countries.

Conclusions:

• Preservatives are a key group of allergens necessitating inclusion in diagnostic testing.
• MCI/MI, while a relatively recent addition, has become a significant contact allergen.
• The incidence of MCI/MI sensitivity aligns with that of other common preservatives, underscoring the importance of awareness and appropriate product formulation.