Contact urticaria caused by Obeche wood (Triplochiton scleroxylon). Report of eight patients.

A variety of plant substances may induce contact urticaria and the list of substances responsible for such reactions is increasing. We report eight patients suffering from occupational asthma caused by Obeche wood sawdust. These patients also presented with urticaria when they worked with this wood. Studies revealed immediate positive skin test reactivity to Obeche wood extracts in all patients. The presence of specific IgE antibodies against Obeche wood could also be demonstrated by a reverse ELISA method. Finally, skin provocation tests (rubbing test) on the eight patients evoked a positive reaction within 20 minutes. These findings strongly suggest an IgE-mediated immunologic mechanism as responsible for the patients' urticaria. Obeche wood should be considered a health hazard capable of causing both bronchial asthma and contact urticaria. At the present time, this timber constitutes the most frequently commercially exported African wood. Many individuals, including carpenters and hobbyists, may come into contact with this wood due to the common use of Obeche wood in the "Do it yourself" type of shops.