SummaryAn allergic reaction, provoked by exposure to the blowflyLucilia cuprinaand shown to be IgE‐mediated, occurred in a subject employed in an entomological research laboratory. The subject's serum, and sera from three other asthmatic patients with IgE antibodies to blowfly extracts, also reacted with extracts from the screw‐worm fly (Chrysomya bezziana). Results suggested that antigens from the two species share immunological cross‐reactivity. Cross‐reactions also exist between the different developmental stages of both species. Allergic reactions to inhaled insect allergens may not be uncommon in the Australian co