We report a 45-year old man who developed maculopapular exanthema on the inferior cervical folder, axillae and umbilicus, as well as erythema multiforme-like lesions on the wrists after the introduction in his work of pao ferro (Machaerium scleroxylon). Patch tests were positive to pao ferro and ebony. This case highlights the importance of patch tests for the confirmation of the culprit agent in occupational dermatoses and also to identify other occupational allergens that the patient should avoid. Tropical woods contain quinones that could explain the possible cross-reactions between woods belonging to different families.