Seven patients who received a lysozyme, nystatin, and tetracycline containing vaginal suppository because of suspected vaginal infection, developed local or systemic allergic reactions. The coincidence of the symptoms with the repeated use of the suppository as well as skin and lymphocyte transformation tests indicated that the lysozyme in the suppository was responsible for the allergic reactions. This lysozyme preparation contained additional egg proteins, which contributed to the allergic reaction in certain patients: three patients with a previous history of egg allergy and serologic and/or skin test evidence for egg-white sensitization developed the allergic reaction after the first suppository. Four patients had urticaria or anaphylaxis after treatment for at least three days; none of these four patients developed egg allergy. Five of seven individuals had positive skin tests (prick or scratch) to ovomucoid and lysozyme, but none of the patients had lysozyme-specific IgE in the circulation. All seven patients, with or without egg allergy, showed vigorous T cell responses to purified lysozyme and partly to other egg-white proteins in the lymphocyte transformation test, which was absent in controls. Vaginal suppositories that contain lysozyme and other contaminating egg white proteins can either elicit allergic reactions in patients with a preexisting egg white allergy or induce sensitization to lysozyme and other egg white components.