Patch testing with constituents of Compositae mixes

Background: The development of mixes containing Compositae plant extracts has improved the diagnosis of Compositae contact allergy, but none of them has fulfilled the criteria for an ideal European plant mix.

Objective: To evaluate which constituents of two commercial Compositae mixes were most useful as screening agents.

Patients: These comprised 76 patients testing positive to Compositae mix 6% in petrolatum and 29 patients testing positive to Compositae mix 5% pet., all of whom were tested with constituents of the respective mixes.

Results: The majority of patients tested positive to parthenolide or parthenolide-containing extracts, followed by German chamomile, yarrow, and arnica. As German chamomile is a weak sensitizer, the results suggest cross-reactions or reactions to unknown allergens. No one was positive to Roman chamomile.

Conclusions: Even though parthenolide seems to be a suitable supplement to the baseline series, the results emphasize that it is important to patch test with extracts of native or locally grown plants, not only because of the geographical variation, but also because of the potential unknown allergens contained in short ether preparations and the variability in the individual patient's exposure and cross-reaction patterns.