Occupational asthma is induced by many agents, including herbal materials, that are exposed in working places. Although there are a few case reports for occupational allergy induced by herbal materials, there is none for that induced by Wonji (Polygala tenuifolia). This study was conducted to evaluate clinical characteristics and immunologic mechanism of Wonji-induced asthma in a exposed-worker. A patient who complained of asthma and rhinitis symptoms, and who had worked in a herbal manufacturing factory for 8 yr, underwent a skin prick test with crude extract of Wonji under the impression of occupational asthma induced by the agent. The patient had a strong positive response to the extract on the skin prick test. Allergen bronchial challenge to the extract demonstrated a typical dual response. Serum specific IgE level to the extract was higher in the patient than in healthy controls, and ELISA inhibition test revealed complete inhibition of IgE binding with the extract, but no inhibition with Der p 2 or mugwort extracts. Six IgE binding components to the extract (10, 25, 28, 36, 50, and 90 kDa) were detected using SDS-PAGE and immunoblot analysis. These findings suggest that Polygala tenuifolia, a herbal material, can induce IgE-mediated bronchoconstriction in exposed workers.