Routine patch testing with the preservative system Kathon CG

Area of Science:

• Dermatology
• Allergology
• Cosmetic Science

Background:

• Allergic contact dermatitis (ACD) is a significant health concern.
• Kathon CG (a mixture of methylchloroisothiazolinone and methylisothiazolinone) is a widely used preservative in consumer products.
• Patch testing is a standard diagnostic tool for ACD.

Purpose of the Study:

• To evaluate the prevalence and relevance of positive patch test reactions to Kathon CG in patients with suspected allergic contact dermatitis.
• To identify common sources of sensitization and clinical presentations associated with Kathon CG allergy.

Main Methods:

• A retrospective analysis of 1620 patients patch tested with Kathon CG (100 p.p.m. aqua).
• Data collection included patient demographics, clinical presentation, dermatitis location, and suspected exposure sources.
• Assessment of reaction relevance to the presenting dermatitis.

Main Results:

• A total of 81 patients (5.0%) showed a positive patch test reaction to Kathon CG.
• Sixty-two reactions (3.8%) were deemed relevant to the patients' clinical condition.
• The majority of affected patients were female, presenting with hand and/or facial dermatitis.
• Cosmetic products were the sensitizing agent in 46% of cases on healthy skin.
• Pre-existing dermatitis, including atopic and irritant dermatitis, was present in 54% of sensitized individuals.
• Moisturizing creams were identified as the most common cause of relevant reactions.

Conclusions:

• Kathon CG is a relevant contact allergen, contributing to allergic contact dermatitis in a notable percentage of patients.
• Awareness of Kathon CG as a potential allergen is crucial for dermatologists and patients, especially those with hand/facial dermatitis or pre-existing skin conditions.
• Further investigation into product formulations and consumer education may help reduce sensitization rates.