PATCH TESTING WITH PRESERVATIVES, ANTIMICROBIALS AND INDUSTRIAL BIOCIDES - RESULTS FROM A MULTICENTER STUDY

Preservatives are biologically reactive substances, and their allergen ic potential has been known for a long time. This study examined the r ole of different preservatives in a large number of patients with susp ected allergic contact dermatitis. Patch test data and data from the p atients' history were collected from the 24 departments participating in the information Network of Departments of Dermatology from 1 Januar y 1990 to 31 December 1994. Patch test data from 28,349 patients teste d with preservatives of the standard series (SS), from 11,485 patients tested additionally with a preservative series (PS), and from 1787 pa tients tested with an industrial biocide tray (IB) were evaluated. Sen sitization rates (standardized) of the SS preservatives were all >1%, with thiomersal rating highest (5.3%), the parabens lowest (1.6%), and the remainder (chlormethylisothiazolinone/methylisothiazolinone, form aldehyde and methyldibromoglutaronitrile/phenoxyethanol (MDBGN/PE)) in the range of 2%. The most important allergens of the PS were, in wome n, alkylaminobenzoate (contained in milking fat) (2.5%), MDBGN/PE (2.2 %), benzalkonium chloride (1.8%), chloracetamide (1.4%), diazolidinyl urea (1.3%), octylgallate (1.2%) and Bronopol(TM) (1.1%). In men rates differed only with regard to alkylaminobenzoate (0.9%). Patients test ed with the IB series reacted most often to methylene-bis-thiocyanate (5%), but with a reaction index of -0.7, many reactions were most prob ably false positives. A further seven preservatives, mostly formaldehy de-releasers used in cutting fluids, gave sensitization rates of betwe en 1% and 3%. Glutaraldehyde, not contained in the series but often te sted additionally, showed a remarkable increase in sensitization durin g the study period. Health care personnel were frequently affected. Al together, this study identified areas of concern within the different groups of preservatives. The overall impact of most of the preservativ es on public health seems to be low, but for diagnostic reasons preser vatives must be included in patch test series.