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Background: Insects are a very diverse group of animals and valuable members of any ecosystem. Allergies to bees and wasps (order: Hymenoptera) are well known in Europe. Allergies, toxicities, and the spread of diseases by other insects are also possible but quite frequently are not diagnosed. Sources: A MEDLINE search on allergy caused by stinging and biting insects apart from bees and wasps was conducted. All relevant articles were evaluated, and a selection of relevant publications and cases from our outpatient units are used to illustrate our arguments. Content and implications: Allergies to insects following bites and stings are common. Ant stings, mainly from imported fire ants, frequently lead to severe anaphylaxis, and their venom can elicit systemic toxic effects. Stings and bites of various other ant species can also lead to severe allergic reactions. Mosquito stings and horsefly or other Diptera stings may elicit severe local and IgE-mediated systemic reactions. True bugs (Hemiptera) are hematophagous insects and can also cause severe allergic reactions, in addition to being feared for transmitting diseases., Allergo Journal International, 31 (6)

Background: Allergies to insect stings and bites are common and were partly discussed in part I of this article series. Other mechanisms leading to allergen contact, sensitization, and potential allergy to insects or insects’ compounds can be hard to suspect and diagnose due to their sometimes-hidden character in food or dust. Aims: We aim to provide an overview of allergic reactions to insects elicited by mechanisms other than sting or bite reactions. Sources: A PubMed search on allergy and insects apart from bees and wasps was conducted, articles were selected and included, and a series of relevant publications and cases of our outpatient units are used as examples. Content and implications: Allergies to insects following direct contact, inhalation, and accidental and deliberate ingestion are common and various insect species can elicit these allergies. Sensitization may occur transcutaneously, upon inhalation, and through ingestion. Allergic reactions to edible insects, such as grasshoppers and mealworms, as genuine allergies or as tropomyosin or other protein cross-reactivities in seafood or house dust mite allergic individuals are possible. In Europe, with the licensing of mealworms to be consumed as food and sold commercially in January 2021, allergies and cross-reactivity to insects or insect compounds as foods will become more common and relevant., Allergo Journal International, 31 (7)

Allergies to gadolinium-based contrast agents (GBCAs) are rare and manifest usually as an immediate drug hypersensitivity reaction (DHR), compatible with an immunoglobulin E (IgE)-mediated mechanism. Although the molecular structures of GBCA show some similarities and are either linear or macrocyclic, the frequency and pattern of cross-reactivity remain unclear. However, cross-reactivity has been described. The aim of this investigation was to assess cross-reactivity in patients with GBCA allergy based on skin tests and exposure. We retrospectively evaluated a total of 28 cases with a proven allergy to a GBCA, including 11 from the database of the allergy division of the Inselspital, Bern and 17 published cases from the literature, retrieved with a PubMed-MEDLINE search. The majority of cases were immediate DHR, with 8/11 cases from the database (72.7%) and 16/17 published cases (94.1%). In both groups macrocyclic GBCA were most often identified as causative drugs. A cross-reactivity based on skin test results was found in 2 out of 11 database cases (18.2%) and in 6 out of 17 literature cases (35.3%). Cross-reactivity occurred within macrocyclic GBCA in 1/11 database cases and 3/17 literature cases, and included both macrocyclic and linear GBCA in 1/11 and 4/17 subjects. There was no cross sensitization among linear GBCA. Skin test-negative GBCA were well tolerated, even in cases with sensitization to linear and macrocyclic GBCA. Overall, cross-reactivity in GBCA allergy is rare (approximately 29%), and may occur among macrocyclic GBCA or in between macrocyclic and linear GBCA. IgE to linear GBCA seems to be rarely cross-reactive. Skin test is helpful in identifying safe alternatives, as no reaction to skin test-negative GBCA was observed.