Severe anaphylactic reaction to thymostimulin.

Thymostimulin is a partially purified extract of calf thymus, consisting of a group of polypeptides with a total molecular weight of approximately 12,000 D. It is used as an immunologic response modifier in primary and secondary immunodeficiencies. We report a patient who had a severe anaphylactic reaction with the first injection of thymostimulin. Type I hypersensitivity to thymostimulin was suggested by an immediate skin test response, specific IgE determination by indirect ELISA and a positive histamine release test. This patient also reacted to bovine serum albumin (BSA), fetal calf serum (FCS) and cow hair and dander. The controls did not react to any of these tests. Clinicians need to be aware that the use of medical products of xenogeneic origin may lead to severe allergic reactions.