Contact allergy to the Asteraceae plant Ambrosia artemisiifolia L (ragweed) in sesquiterpene lactone-sensitive patients in southern Sweden.

Ambrosia artemisiifolia L. a classical cause of ragweed dermatitis in North America, is also found in Europe. 17 patients with contact allergy to sesquiterpene lactone (SL) mix were recalled for patch testing with extracts of North American and Swedish ragweed, the latter harvested in summer and autumn. 8/17 patients were test-positive to the American extract, 14/17 to the Swedish summer extract and 15/17 to the autumn extract. All patients except 1 were found to have a chronic hand eczema of the pompholyx type. 5/16 hand eczema patients had a flare-up of their pompholyx at patch testing. We concluded that patients with SL mix allergy are allergic to American as well as to Swedish ragweed. Pompholyx seems to be a frequent clinical picture in patients with SL mix allergy.