[Allergy to isothiazolinones in recent years]

Area of Science:

• Dermatology
• Occupational Medicine
• Toxicology

Background:

• Isothiazolinones are widely used preservatives in cosmetics and industrial products.
• Methylisothiazolinone (MI) replaced the MCI/MI mixture (Kathon CG) in many applications.
• Increased contact dermatitis cases led to MI restrictions in cosmetics.

Purpose of the Study:

• To analyze the incidence of contact allergy to isothiazolinones.
• To evaluate patch test results and hypersensitivity related to occupation.
• To assess the contribution of immediate allergy to isothiazolinone hypersensitivity.

Main Methods:

• Patch tests with methylchloroisothiazolinone/methylisothiazolinone and methylisothiazolinone were performed on 1137 patients.
• Prick tests with methylisothiazolinone were conducted on 29 patients with confirmed allergy.
• Study period: 2014-2018 at the Nofer Institute of Occupational Medicine.

Main Results:

• 95 out of 1137 patients (8.3%) showed allergy to isothiazolinones.
• Positive patch tests were higher for methylisothiazolinone alone (7.8%) than Kathon CG (5.4%).
• Occupations with high sensitization included office workers, medical staff, mechanics, and construction workers.

Conclusions:

• Isothiazolinones, particularly methylisothiazolinone, are significant causes of contact allergy, including occupational allergies.
• These compounds exhibit strong allergenic properties, often causing severe reactions in patch tests.
• The role of immediate allergy in isothiazolinone sensitization requires further investigation.