An 8-year experience with routine SL mix patch testing supplemented with Compositae mix in Denmark

Routine patch testing with sesquiterpene lactone (SL) mix, supplemented wit h Compositae mix (CM) and other Compositae extracts and allergens where app ropriate, was evaluated over an 8-year period. 190 of 4386 patients tested (4.3%) were Compositae-sensitive, 143 females (mean age 51.5 years) and 47 males (mean age 55 years), and 83% of reactions considered clinically relev ant. 22% were suspected of occupational sensitization/dermatitis. 62% had a contact allergy to 2 or more compounds, most often to nickel, fragrance an d colophonium. SL mix detected 65%, CM 87% of Compositae-allergic patients, and the overall detection rate with both mixes was 93%. Few irritant react ions and no cases of dear-cut active sensitization were recorded with the m ixes, but our results emphasize the importance of differentiating late-appe aring reactivation reactions from patch test sensitization. The weakly posi tive CM reactions could reflect some irritancy, but as they were associated with fragrance and/or colophonium allergy to a higher degree than weakly p ositive SL mix reactions, they probably represented cross-reactions. In con clusion, the detection rate with SL mix was high enough to support its cont inued use as a screening mix and it was very well and rather safely supplem ented by aimed testing with CM.