Compositae dermatitis confined to exposed skin has often been considered on clinical grounds to be airborne. Although anecdotal clinical and plant chemical reports suggest true airborne allergy, no proof has been procured. Feverfew (Tanacetum parthenium) is a European Compositae plant suspected of causing airborne contact allergy, and its most important allergen is the sesquiterpene lactone (SQL) parthenolide (PHL).Objectives
The aims of this study were to (i) assess the allergenicity of feverfew-derived monoterpenes and sesquiterpenes and their oxidized products in feverfew-allergic patients and (ii) re-assess the role of PHL and other SQLs in airborne contact allergy.Patients and methods
Feverfew-allergic patients were patch tested with extracts and fractions containing volatile monoterpenes and sesquiterpenes as well as extracts of airborne particles from flowering feverfew plants, obtained by fractionation of ether extracts, dynamic headspace and high-volume air sampler (HIVAS) technique, respectively.Results
Among 12 feverfew-allergic patients, eight had positive patch-test reactions to a HIVAS filter extract, while two tested positive to a headspace extract. Subsequent analysis of the HIVAS extract by gas chromatography and mass spectrometry detected PHL in a concentration of 510 ng mL−1 in the HIVAS extract. Testing with a dilution series of PHL showed positive reactions down to 8·1 ng in selected patients. None of the 12 patients tested positive to monoterpenes or sesquiterpenes, whether they were oxidized or not.Conclusions
The clinical results have proved that some feverfew-allergic patients are sensitive to airborne particles released from the plant, and isolation of PHL from the particle-containing HIVAS extract in allergenic amounts is strong evidence of PHL as the responsible allergen.