Contact Dermatitis to Inula viscosa Aiton

A 55-year-old rural worker complained of eczematous dermatitis of the dorsa of the hands over a period of 5 years. Dermatitis had been relapsing in midsummer upon contact with a plant identified as Inula viscosa Aiton and had been spreading over the face and forearms over the last 2 years. Whereas patch tests to aqueous and ethanolic extracts of the whole plant gave irritant reactions, patch tests to alantolactone and isoalantolactone gave allergic positive reactions. Repeated thin layer chromatography of the chloroformic extracts of the stem and leaves identified five fractions that all gave irritant reactions to patch test at 10-3 and 10-4 concentrations. At 10-5 and 10-6 concentrations, only two fractions gave positive allergic reactions. A careful 1H and 13C nuclear magnetic resonance analysis of these repeatedly chromatographically purified two fractions allowed us to isolate the compound clearly predominant in each of them. Although present in this plant population in different amounts, these compounds were those identified by Bohlmann et al as 2-deacetoxyxanthinin 1 (xanthinosin) and Inuvisculide 2. Both these sesquiterpenelactones were found to be the strong sensitizing agents of viscosa Aiton.