The spectrum of allergic (cross-)sensitivity in clinical patch testing with 'para amino' compounds.

BACKGROUND

Allergic contact sensitization to 'para amino' compounds is frequent and the spectrum of cross-reactivity between members of this chemical group is variable.

METHODS

A retrospective analysis of clinical patch test data obtained with a special test series in the centres of the Information Network of Departments of Dermatology (IVDK) between 1995 and 1999.

RESULTS

In the 638 patients tested with the above test panel positive reactions were observed most often to p-aminoazobenzene (16.2%), p-phenylenediamine (14.1%), p-toluylenediamine (10.0%), followed by 4,4'-diaminodiphenylmethane (8.5%), Disperse Orange 3 (8.4%) and p-aminophenol (3.1%). Among the 544 patients tested with p-phenylenediamine and all seven additional 'para amino' compounds, concordance between reactions varied greatly. The stronger the positive test reaction to p-phenylenediamine, p-toluylenediamine or p-aminoazobenzene, the more frequently additional positive reactions to the other compounds were observed.

CONCLUSIONS

A screening employing several 'para amino' compounds is necessary to describe the individual spectrum of allergic contact sensitization, as there is no reliable marker substance. Further research should aim at (i) establishing the mechanism of cross-reactivity to 'para amino' compounds and (ii) identifying exposures in the environment.