Contact Allergy to Polyhexamethylene Biguanide (Polyaminopropyl Biguanide).

BACKGROUND Polyaminopropyl biguanide (INCI name) and polyhexamethylene biguanide (PHMB) are polymeric biguanides. PHMB is a broad-spectrum antimicrobial substance used as a preservative in many products. Due to our limited knowledge on PHMB contact allergy frequency and the fact that cases of allergic contact dermatitis to PHMB might be missed, we included PHMB as a screening allergen since 2016. OBJECTIVE To report the prevalence of positive patch test reactions to PHMB as a screening allergen in suspected allergic contact dermatitis patients. METHODS A retrospective analysis of 1760 patch tested patients from July 2016 to December 2018 was performed. Polyaminopropyl biguanide (2.0% in water) was included in the extended Malmo baseline series during the study period. RESULTS Of all patients, 1204 (68.4%) were female. Positive patch test reactions were reported in 19 (1.1%) patients. The most common sites of lesions were face, head and neck (52.6%). There was a significant correlation between concomitant reactions to PHMB and other cosmetic-related allergens. CONCLUSION The prevalence of positive reactions to PHMB was higher than previously reported. Patch testing with PHMB should be performed in dermatitis patients with lesions on the face, head and neck. This article is protected by copyright. All rights reserved.