The coumarin herniarin as a sensitizer in German chamomile [Chamomilla recutita (L.) Rauschert, Compositae].

Although German chamomile (Chamomilla recutita) is considered a weak sensitizer, recent studies have shown several possible non-sesquiterpene lactone allergens in tea (infusions) from the plant. The aim of this study was to report the results of patch testing with herniarin (7-methoxycoumarin), which is one of the possible coumarin allergens in chamomile. Between 1991 and 2009, selected patients with known or suspected Compositae contact allergy were patch tested with herniarin 1% petrolatum. Among 36 patients tested, there was one positive and three doubtful positive reactions to herniarin. All 4 patients had a relevant contact allergy to German chamomile, whereas the majority of the remaining 32 patients had chamomile allergy of unknown relevance. The clinical results suggest that herniarin indeed is one of the non-sesquiterpene lactone sensitizers in German chamomile and that sensitization may occur through, for example, external use of chamomile tea or use of chamomile-containing topical herbal remedies.