Epikutantest-Reaktionen auf Paraben-Mixe und ihre Aufschlüsselungen. Studien der Deutschen Kontaktallergie-Gruppe (DKG) und des Informationsverbundes dermatologischer Kliniken (IVDK), 1990 – 2000

Abstract

Parabens are commonly used preservatives in topical preparations, including cosmetics, in medicines, and in food. They are capable of inducing contact sensitisation, especially in patients with stasis dermatitis. Between 1990 and 1994, a mix containing 5 parabens (benzyl-, butyl-, ethyl-, methyl- and propylparaben, 3% each) was used for diagnostic patch testing. Of 23025 patients tested with this mix, 1.6% had positive test reactions. In break-down testing with single constituents (tested with 3%) mainly benzyl paraben, which was not tested (and not used) due to possible carcinogenic risk any more, and propyl caused positive test reactions (in 10 of 184 and 13 of 616 patients, respectively). The sensitivity of the mix with regard to detecting contact allergy to one (or more) of the constituents was 88% and specifity 96%; however, the positive predictive value (PPV) was only 23%, i.e., about 3/4 false-positive reactions occurred. In a subsequent study of the German Contact Dermatitis Research Group (DKG) 1286 patients were patch tested with the above mentioned mix, which had to be replaced, and 2 mixes (4 x 3% and 4 x 4%) containing the remaining parabens; positive reactions were observed in 2.1%, 1.2% and 1.5%, respectively. The sensitivity of the new mixes was lower (47% and 53%, resp.), however, the PPV (44% and 42%, resp.) was more acceptable. Between 1995 and 2000 altogether 51260 patients were patch tested with the standard series, including the 4 x 4% paraben-mix in the IVDK centres, with 1.5% positive reactions. Break-down testing was performed in 1270 of these. The diagnostic performance of the mix found here (sensitivity: 78%, PPV: 44%) was similar to that in the DKG-study. In conclusion, patch testing with parabens is still difficult, in particular, as several paraben paradoxes hamper the application of a valid gold standard (e.g., a repeated open application test [ROAT] on uninvolved skin) when judging patch test reactions. Despite these limitations in risk assessment, parabens can be regarded as relatively safe, although this benefit is somewhat limited by the necessity to add other - potentially more sensitising - biocides to achieve adequate protection against microbial decay in some products.