Ramie (Boehmeria nivea) pollen-induced bronchial asthma and allergenic cross-reactivity of ramie and Parietaria.

Ramie (Boehmeria nivea), a plant of the Urticaceae family, is widely distributed in the Nagasaki area, and has been established to be a cause of asthma. The rate of positive reactions to ramie in intradermal tests was 11.7% among adult asthmatic patients in the Nagasaki area. In this study, 10 patients were positive in provocation tests using ramie pollen. Ramie pollen-specific IgE antibodies were measured by ELISA, with the positive provocation test group showing higher O.D. values than the positive intradermal test group (p < 0.05). Ramie is of the same family as Parietaria, an important allergen in Europe. The cross-reactivity of ramie and Parietaria was examined by an ELISA inhibition test using P. officinalis and P. judaica (Pj10), but no cross-reactivity was found, suggesting that ramie may be a new independent allergen. As ramie is widely distributed throughout Japan and South-east Asia, further study is needed to determine whether it is an important allergen of the Urticaceae family in this region, as is Parietaria in Europe, and Urtica in America.