For some years, biological pest control has been re-evaluated as an alternative to the indiscriminate use of pesticides. The number of "bio-factories" in Europe has been constantly increasing and today more than 100 technicians work in mass rearing of arthropods. Seven cases of asthma and allergic rhinitis are reported in 13 workers engaged in the production of beneficial arthropods. The subjects suffered from attacks of asthma and rhinitis when they came into contact with eggs and scales or waste of Chrysoperla carnea, Leptinotarsa decemlineata, Ostrinia nubilalis and Ephestia kuehniella. These attacks occurred after an average exposure period of 18 months. A RAST test, prepared by Lofarma, was carried out on subjects' serum against the above-mentioned allergens and was positive in all symptomatic subjects (7 of 13) and negative in the others. This demonstrates IgE direct sensitization mediated by complete antigens.