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From a taxonomic point of view, Hymenoptera are subclassified into families: Apidae, including honeybees (Apis mellifera) and bumblebees (Bombus), and Vespidae, which, in turn, are divided into the subfamilies of Vespinae (wasps, including hornets, vespules, dolichovespules) and Polistinae (paper wasp). Hypersensitivity to Hymenoptera venom can be linked to immunological (IgE-mediated or non-IgE-mediated) and non-immunological mechanisms. Reactions are classified into local reactions, large local reactions, systemic reactions, toxic reactions, and unusual reactions. In general, children sensitize less frequently and have less severe reactions than adults, probably due to less exposure to repeated stings and fewer comorbidities. There are risk factors for systemic reactions that should be discussed with patients and their parents as appropriate. A correct diagnosis of Hymenoptera venom allergy relies on a careful clinical history and the appropriate use of skin and in vitro tests. The in vitro tests include serum specific IgE toward venom extracts and toward allergenic molecules. In complex diagnoses, CAP-inhibition and the Basophil Activation Test can also be used. In the presence of a systemic reaction, the basal serum tryptase measurement should be performed to rule out mastocytosis. In case of allergic reactions to Hymenoptera stings, in the acute phase, according to the current guidelines, the treatment of signs and symptoms mainly includes the use of adrenaline as first-line treatment in case of anaphylaxis and antihistamines and corticosteroids as subsequent lines of treatment. Given the impossibility of avoiding a new sting with certainty, the treatment of choice in subjects with hypersensitivity to Hymenoptera venom who have experienced systemic reactions is based on venom immunotherapy (VIT), with the venom of the responsible stinging insect identified after an adequate allergological work-up. VIT is performed in a suitable environment and has proved to be safe and effective with various administration protocols, both accelerated and conventional. The prevention of Hymenoptera venom anaphylaxis in patients who have already developed a previous episode is crucial and must be supported by environmental protection interventions and early therapy. Places where one is more likely to encounter insects and risky behaviors should be avoided. [ABSTRACT FROM AUTHOR]

Background: Large local reactions (LLR) to Hymenoptera stings were considered as IgE-mediated late-phase inflammatory reactions. However, in older studies, most patients with LLR were skin test positive, but only around 50% had detectable sIgE determined by the RAST system. Methods: Data of 620 patients were evaluated retrospectively: 310 patients who suffered from LLR and 310 patients with previous systemic sting reactions (SSR). We aimed to clarify if sIgE can generally be detected by the CAP system in patients with LLR; sIgE levels and clinical parameters were compared between patients with LLR and SSR. Results: Positive sIgE levels were detected in 80.7% of patients with LLR, and in 95.2% of patients with SSR (p<0.001). Of the 310 patients with LLR, 80.6% had a LLR with a size of 10-20cm, whereas 19.4% had swellings >20cm, with a mean duration of seven days. In only 2.9% of patients, LLRs occurred after stings on the trunk, while 14.8% of SSR resulted from stings on this site (p<0.001). Similarly, LLR were also less frequent on the capillitium compared to SSR (8.1% versus 26.2%; p = 0.035) Conclusions: LLR usually persisted over seven days and about one fifth of patients had swellings greater than 20cm. Contrary to SSR, LLR were less frequently observed on the capillitium and on the trunk. In most patients with LLR, sIgE could be detected. However, total IgE and sIgE levels to bee or vespid venom did not differ between patients with LLR and SSR. [ABSTRACT FROM AUTHOR]