Patch testing for Compositae allergy.

The main allergenic constituents of Compositae plants are the sesquiterpene lactones (SLs). In recent years, a mixture of three SLs, each with a different sesquiterpene skeleton (alantolactone, dehydrocostuslactone or costunolide), has been routinely used to detect Compositae allergy. The purpose of our study was to establish the value of testing with a range of Compositae extracts. Ninety-seven consecutive patients with exposure pattern dermatitis or hand eczema and gardening as a hobby or occupation were patch tested to the European standard series including SL mix 0.1% pet., Compositae extracts and other relevant allergens. Twenty-six of the 97 patients tested showed allergic reactions to SL mix or Compositae extracts. Fifteen of these showed positive reactions to both the SL mix and Compositae extracts. Eleven patients showed a negative reaction to the SL mix but positive reaction to the Compositae extracts. Dandelion elicited a positive reaction in eight of the 11 SL mix-negative patients and three patients reacted to feverfew. The SL mix failed to detect 38% of our Compositae-sensitive patients. Dandelion extract alone detected 73% of SL-negative patients. Additional testing with feverfew extract would have detected 91% of the SL mix-negative individuals. Our study highlights the importance of testing the response of SL-negative patients to additional Compositae extracts when there is a clinical suspicion of Compositae allergy.