Beta-lactam drugs can induce allergic immune responses due to their antigenic determinants, promoting IgE-binding and anaphylactic reactions to penicillin. We report a case of a 44-year-old woman who experienced several severe systemic reactions after being exposed directly or indirectly to penicillin. An anaphylactic shock occurred after anal installation of her daughter's urine, who had been treated with penicillin. Skin testing revealed immediate type reactions to major and minor determinants of penicillin indicating an IgE-mediated sensitization. In vitro tests showed elevated levels of penicillin specific IgE. Clinical features, difficulties in taking history and test options for patients with IgE-mediated sensitizations are briefly reviewed in the context of the presented case of unexpected reactions to penicillin due to an immediate type hypersensitivity.