Patients A and M developed allergic symptoms when working in a greenhouse with paprika plants and freesia plants, respectively. The possible involvement of an IgE-mediated mechanism was investigated with the skin prick test, radioallergosorbent test (RAST) and the histamine release test (HRT). Paprika flower, leaf and stem extract released 58, 47 and 43% of the total amount of histamine from washed leukocytes of patient A. In serum A IgE antibodies against paprika leaves and flowers could be demonstrated by RAST (11% binding of 125I-anti-IgE added). Freesia flower and stem extract released 46 and 43% histamine, respectively, from washed leukocytes of patient M. In the RAST, specific IgE antibodies against freesia flowers and stems were found in serum M (37% binding of 125I-anti-IgE added).