Background: Furry animals produce allergens that can cause allergic rhinitis and asthma. In contrast, scaly animals, such as lizards, are assumed not to be allergenic. Objective: We sought to evaluate a 32-year-old man who complained of allergic rhinitis and asthma symptoms that occurred exclusively in his own home. He had dogs and cats at home but denied any increase in symptoms specifically associated with these pets. Skin prick testing initially performed to 42 common aeroallergens, including cat, dog, and house dust mite, elicited negative results. He later reported that the symptoms were worse on exposure to his pet iguanas. Methods: Skin prick tests were subsequently performed to an extract made from scales from his pet iguana. Extracts were also prepared from several zoo reptiles. Immunoassays for IgE antibody, as well as IgE immunoblots, were performed by using these extracts and the patient's serum. Results: The skin prick test result with the pet iguana scale extract was positive. The patient's serum contained IgE antibody to his own pet iguana and to a zoo iguana. Conclusion: Our patient's history, skin test results, and in vitro studies clearly demonstrate that he is allergic to iguana. Physicians should be aware that such allergy to scaly pets may occur and should not restrict history taking to questions about furry pets. (J Allergy Clin Immunol 2000;106:369-72.)