Two cases of cross-sensitivity in subjects allergic to paraphenylenediamine following ingestion of Polaronil.

We report the cases of 2 women presenting allergy to paraphenylenediamine (PPD). Both patients had a history of eczema that worsened following the ingestion of the antihistamine Polaronil (dexamethasone/dexchlorpheniramine). This clinical presentation could be explained by cross-sensitivity to sulfanilic acid (4-aminobenzene sulfonic acid), a metabolite of sunset yellow (FD&C No. 6). Sunset yellow is an azo dye present in this tablet. Indeed, PPD-allergic subjects may suffer from cross-sensitivity to related compounds, especially to those that can be ingested such as azo dyes. Such compounds are used in some instances by the food and pharmaceutical industries, but their presence is often undisclosed.