FS04.5 Iodopropynylbutyl carbamate (IPBC) 0.2% is suggested for patch testing of patients with eczema possibly related to preservatives

Abstract

Iodopropynylbutyl carbamate (IPBC)is a preservative that has been increasingly used for skin care products and cosmetics within the last years and the first cases of contact sensitization have meanwhile been reported. Therefore, a surveillance for IPBC contact allergy is now necessary. Our study was aimed to find out a suitable test concentration of IPBC for this purpose. The data 8106 patients tested by 23 centres of the German Contact Dermatitis Research Group (DKG) and the Information Network of Departments of Dermatology (IVDK)in the time from May 2001 to July 2003 with IPBC in concentrations of 0.1%, 0.2%, 0.3%, and 0.5% were retrospectively evaluated. Criteria considered to determine the optimal test concentration of IPBC were the reaction index, the positivity ratio, the rate of crescendo reactions, and the relation of IPBC‐reactions with MOAHLFA‐indices, with irritant reactions to sodium lauryl sulfate, and with positive reactions to the most common standard contact allergens and 4 other preservatives. For statistical evaluations the exact McNemar test was applied and odds ratios were calculated according to the profile likelihood method, as derived from logistic regression analyses. The rate of positive reactions to IPBC increased from 0.5% with IPBC 0.1% to 1.7% with IPBC 0.5%, but there was a problem with sensitivity or specificity with both of these 2 concentrations. Therefore, we focused on IPBC 0.2%(0.8% positive reactions) and IPBC 0.3%(1.3% positive reactions) for further detailed analyses. An evaluation of the related parameters revealed that with IPBC 0.2% as compared to IPBC 0.3% a higher percentage of crescendo reactions, a higher reaction index, a lower number of doubtful reactions, a plausible association of positive reactions with reactions to other preservatives, nd no association with a pronounced skin irritability was found. In conclusion, we recommend to start with IPBC 0.2% for patch testing of all persons with contact dermatitis that may be related to preservatives.