Standardized allergen extracts for allergen immunotherapy.

Nineteen U.S. allergen extracts were standardized by the U.S. Food and Drug Administration (FDA) between 1987 and 1998, including of two house-dust mites, short ragweed, cat hair and cat pelt, seven temperate and one southern grass, and six Hymenoptera venom preparations. Relevant literature was reviewed. For each allergen, a "representative" extract was established; the potency of each representative extract was determined by measurement of the total protein content (Hymenoptera venom), radial diffusion measurement of the dominant allergen (short ragweed and cat), or, if there was no dominant allergen, then by quantitative skin testing by using the ID50EAL (intradermal dilution for 50 mm sum of erythema determines the bioequivalent allergy units) method. In vitro tests were developed to allow the manufacturer to demonstrate that each lot of its extract was statistically identical, within defined limits, to the FDA reference extract. These tests included radial immunodiffusion, competitive enzyme-linked immunosorbent assay, and isoelectric focusing. The standardized extracts offer the advantage of consistent potency from lot to lot for each manufacturer and also from manufacturer to manufacturer, and assure the presence of recognized significant allergens within the extract. Therefore, standardized extracts offer improved safety and efficacy over their nonstandardized predecessors.

Immunomic Investigation of Holocyclotoxins to Produce the First Protective Anti-Venom Vaccine Against the Australian Paralysis Tick, Ixodes holocyclus.

Venom producing animals are ubiquitously disseminated among vertebrates and invertebrates such as fish, snakes, scorpions, spiders, and ticks. Of the ~890 tick species worldwide, 27 have been confirmed to cause paralysis in mammalian hosts. The Australian paralysis tick (Ixodes holocyclus) is the most potent paralyzing tick species known. It is an indigenous three host tick species that secretes potent neurotoxins known as holocyclotoxins (HTs). Holocyclotoxins cause a severe and harmful toxicosis leading to a rapid flaccid paralysis which can result in death of susceptible hosts such as dogs. Antivenins are generally polyclonal antibody treatments developed in sheep, horses or camels to administer following bites from venomous creatures. Currently, the methods to prevent or treat tick paralysis relies upon chemical acaricide preventative treatments or prompt removal of all ticks attached to the host followed by the administration of a commercial tick-antiserum (TAS) respectively. However, these methods have several drawbacks such as poor efficacies, non-standardized dosages, adverse effects and are expensive to administer. Recently the I. holocyclus tick transcriptome from salivary glands and viscera reported a large family of 19 holocyclotoxins at 38-99% peptide sequence identities. A pilot trial demonstrated that correct folding of holocyclotoxins is needed to induce protection from paralysis. The immunogenicity of the holocyclotoxins were measured using commercial tick antiserum selecting HT2, HT4, HT8 and HT11 for inclusion into the novel cocktail vaccine. A further 4 HTs (HT1, HT12, HT14 and HT17) were added to the cocktail vaccine to ensure that the sequence variation among the HT protein family was encompassed in the formulation. A second trial comparing the cocktail of 8 HTs to a placebo group demonstrated complete protection from tick challenge. Here we report the first successful anti-venom vaccine protecting dogs from tick paralysis.

Characterization of New Allergens from the Venom of the European Paper Wasp Polistes dominula.

Discriminating Polistes dominula and Vespula spp. venom allergy is of growing importance worldwide, as systemic reactions to either species' sting can lead to severe outcomes. Administering the correct allergen-specific immunotherapy is therefore a prerequisite to ensure the safety and health of venom-allergic patients. Component-resolved diagnostics of Hymenoptera venom allergy might be improved by adding additional allergens to the diagnostic allergen panel. Therefore, three potential new allergens from P. dominula venom-immune responsive protein 30 (IRP30), vascular endothelial growth factor C (VEGF C) and phospholipase A2 (PLA2)-were cloned, recombinantly produced and biochemically characterized. Sera sIgE titers of Hymenoptera venom-allergic patients were measured in vitro to assess the allergenicity and potential cross-reactivity of the venom proteins. IRP30 and VEGF C were classified as minor allergens, as sensitization rates lay around 20-40%. About 50% of P. dominula venom-allergic patients had measurable sIgE titers directed against PLA2 from P. dominula venom. Interestingly, PLA2 was unable to activate basophils of allergic patients, questioning its role in the context of clinically relevant sensitization. Although the obtained results hint to a questionable benefit of the characterized P. dominula venom proteins for improved diagnosis of venom-allergic patients, they can contribute to a deeper understanding of the molecular mechanisms of Hymenoptera venoms and to the identification of factors that determine the allergenic potential of proteins.

The Diagnostic Importance of Recombinant Allergen IgE Testing in Patients with Hymenoptera Venom Allergy: Comparison of Two Methods.

Adults with systemic anaphylactic reactions (SAR) to insect sting show often multiple-positivity of serum-specific IgE (sIgE) to Hymenoptera venoms. Unnecessary long-lasting venom-specific immunotherapies (VIT) in false-positive patients increase the risk of recurrent SAR. This report aims to analyze the diagnostic importance of recombinant allergen IgE testing in patients with SAR to Hymenoptera sting. In 82 patients we measured sIgE to honeybee venom (HBV), wasp venom (WV) and hornet venom (HV) extracts, recombinant phospholipase A2 from HBV (sIgE-rApi m1), recombinant antigen 5 from WV (sIgE-rVes v5), and cross-reactive carbohydrate determinants-CCD-bromelain by ImmunoCAP. We analyzed the correlation of ImmunoCAP and Immunoblot for HBV and WV extracts, rApi m1, and rVes v5 in 39/82 patients. According to the history of the culprit insect, we compared sensitivity and specificity between the two methods. The severity of the SAR does not depend on the sIgE level to venom extracts and recombinant allergens. Fifty-one percent of the patients had a multiple-positivity to HBV/WV or HBV/WV/HV extracts. Severe SAR and CCD-sIgE were more frequent in multiple-positive than single-positive patients. CCD-sIgE were more frequent in HBV allergic patients than WV and HV allergic patients. There was a significant correlation between levels of sIgE to venom extracts and recombinant allergens measured by ImmunoCAP and Immunoblot. ImmunoCAP has higher sensitivity and specificity than Immunoblot for diagnosis of SAR to Hymenoptera venoms. IgE testing to recombinant CCD-free allergens is necessary for the adequate selection of long-lasting VIT, especially in patients with multiple sensitivities to venom extracts.

Hymenoptera Venom Immunotherapy: Immune Mechanisms of Induced Protection and Tolerance.

Hymenoptera venom allergy is one of the most severe allergic diseases, with a considerable prevalence of anaphylactic reaction, making it potentially lethal. In this review, we provide an overview of the current knowledge and recent findings in understanding induced immune mechanisms during different phases of venom immunotherapy. We focus on protection mechanisms that occur early, during the build-up phase, and on the immune tolerance, which occurs later, during and after Hymenoptera venom immunotherapy. The short-term protection seems to be established by the early desensitization of mast cells and basophils, which plays a crucial role in preventing anaphylaxis during the build-up phase of treatment. The early generation of blocking IgG antibodies seems to be one of the main reasons for the lower activation of effector cells. Long-term tolerance is reached after at least three years of venom immunotherapy. A decrease in basophil responsiveness correlates with tolerated sting challenge. Furthermore, the persistent decline in IgE levels and, by monitoring the cytokine profiles, a shift from a Th2 to Th1 immune response, can be observed. In addition, the generation of regulatory T and B cells has proven to be essential for inducing allergen tolerance. Most studies on the mechanisms and effectiveness data have been obtained during venom immunotherapy (VIT). Despite the high success rate of VIT, allergen tolerance may not persist for a prolonged time. There is not much known about immune mechanisms that assure long-term tolerance post-therapy.

Prevalence of mastocytosis and Hymenoptera venom allergy in the United States.

BACKGROUND: Mastocytosis is a risk factor for Hymenoptera venom anaphylaxis (HVA). Current guidelines recommend measuring tryptase in patients with HVA and that those with mastocytosis pursue lifelong venom immunotherapy (VIT). Available data on HVA and mastocytosis largely derive from European single-center studies, and the prevalence of HVA with and without mastocytosis in the United States is unknown. OBJECTIVE: We sought to determine the prevalence of HVA and mastocytosis in the United States using an insurance claims database and evaluate the impact of mastocytosis on VIT in patients with HVA in a US cohort. METHODS: The IBM Watson Database, consisting of insurance claims from approximately 27 million US patients in 2018, was queried to identify patients with HVA and/or mastocytosis. Furthermore, a retrospective study of 161 patients undergoing VIT between 2015 and 2018 at the University of Michigan was conducted. RESULTS: In the IBM Watson Database, the prevalence of HVA was 167 per 100,000 (0.167%) and the prevalence of mastocytosis 10 per 100,000 (0.010%) overall and 97 per 100,000 (0.097%) among those with HVA. Mastocytosis showed a 9.7-fold increase among patients with HVA versus the general population. In the U-M cohort, 2.6% of patients with VIT had mastocytosis. Tryptase level did not correlate with venom reaction severity but was higher in patients with systemic VIT reactions. CONCLUSIONS: We observed a lower US HVA prevalence than previously reported. Mastocytosis was more common in US patients with HVA, though at lower rates than previously reported. In patients with VIT there was no correlation between tryptase level and reaction severity.

Precision Medicine in Hymenoptera Venom Allergy: Diagnostics, Biomarkers, and Therapy of Different Endotypes and Phenotypes.

Allergic reactions to stings of Hymenoptera species may be severe and are potentially fatal deviations of the immunological response observed in healthy individuals. However, venom-specific immunotherapy (VIT) is an immunomodulatory approach able to cure venom allergy in the majority of affected patients. An appropriate therapeutic intervention and the efficacy of VIT not only depend on a conclusive diagnosis, but might also be influenced by the patient-specific manifestation of the disease. As with other diseases, it should be borne in mind that there are different endotypes and phenotypes of venom allergy, each of which require a patient-tailored disease management and treatment scheme. Reviewed here are different endotypes of sting reactions such as IgE-mediated allergy, asymptomatic sensitization or a simultaneous presence of venom allergy and mast cell disorders including particular considerations for diagnosis and therapy. Additionally, phenotypical manifestations of venom allergy, as e.g. differences in age of onset and disease severity, multiple sensitization or patients unsusceptible to therapy, are described. Moreover, biomarkers and diagnostic strategies that might reflect the immunological status of the patient and their value for therapeutic guidance are discussed. Taken together, the increasing knowledge of different disease manifestations in venom hypersensitivity and the growing availability of diagnostic tools open new options for the classification of venom allergy and, hence, for personalized medical approaches and precision medicine in Hymenoptera venom allergy.

The effect of hymenoptera venom immunotherapy on neutrophils, interleukin 8 (IL-8) and interleukin 17 (IL-17).

OBJECTIVES: Venom immunotherapy (VIT) is an effective treatment method and is addressed to patients with a history of an anaphylactic reaction to Hymenoptera stings. However, the immunological mechanisms of protection have not been explained yet. The objective of this study was to analyze neutrophils, interleukin 8 (IL-8) and interleukin 17 (IL-17) before and after the initial phase of the immunotherapy. MATERIAL AND METHODS: Overall, 40 individuals, including 20 wasp venom sensitized and 20 bee venom sensitized patients, were included in the study. The patients had had a history of severe allergic reactions type III and IV according to Mueller's classification. An ultra-rush VIT protocol was used in this study. The concentration of serum IL-8 and IL-17A was determined using the ELISA enzymatic method. RESULTS: The authors demonstrated a significant rise in the IL-8 level after the immunotherapy, compared to baseline (14.9 vs. 24.7, p < 0.05). The rise in the neutrophils level was also noticeable but proved to be barely out of the range of statistical significance (4.3 vs. 5.0, p = 0.06). The shift in IL-17A was negligent and not statistically significant in the paired samples t-test (1.6 vs. 1.5, p = 0.34). CONCLUSIONS: Venom immunotherapy induces neutrophils and IL-8 activity after 2 days. After the desensitization, the level of IL-17A did not change. Int J Occup Med Environ Health. 2020;33(6):811-7.

Hymenoptera allergy and anaphylaxis: are warmer temperatures changing the impact?

PURPOSE OF REVIEW: Climate change has brought about many changes in our ecosystem. Prolongation of pollen seasons has been reported, related to earlier frost off in the spring and later onset of frost on in the fall. This review considers recent global evidence that stinging insects are redistributing toward the poles, thereby potentially increasing human exposure and risk of sting events. RECENT FINDINGS: With changing climate, particularly climate warming, range expansion of insects is occurring in both the Northern and Southern Hemispheres. Likewise, stinging insects, such as Hymenoptera and Lepidoptera, are also expanding range. Though there is scant data on associated increase of insect-related anaphylaxis, increased insect-human interaction is certain. SUMMARY: It is likely that climate change will continue to alter the distribution and population of Hymenoptera and other insects. As temperatures warm and regions become suitable for nesting and establishment of colonies, many insects will expand their territory. As already reported in Alaska, one would anticipate expansion of range, especially toward the poles, thereby increasing the probability of human encounters and likewise anaphylaxis.

Pregnancy and Hymenoptera venom allergy.

PURPOSE OF REVIEW: To evaluate the indication to perform venom immunotherapy (VIT) during pregnancy considering the risks of adverse events during the build-up phase or the maintenance phase and analyzing specific articles and guidelines on VIT. RECENT FINDINGS: Only few studies treat this argument and literature only counts one recent study on the topic, whereas recent guidelines state the behavior to keep in pregnancy. SUMMARY: Hymenoptera venom allergy (HVA) affects about 7.5% of the European population. VIT is the only effective disease-modifying treatment for patients presenting anaphylactic reactions. VIT counts several mechanisms of action, with the increase of IgG1 and IgG4 and a cytokine impairment inducing a Th2-Th1 shift. Pregnancy is a health condition where a Th2 profile is required to prevent fetal rejection, so VIT could be a problem for the fetus when started during pregnancy.

Natural history and long-term follow-up of Hymenoptera allergy.

PURPOSE OF REVIEW: Information on the natural history of hypersensitivity reactions is helpful for deciding which patient urgently needs a venom immunotherapy (VIT). RECENT FINDINGS: The frequency of self-reported systemic allergic reactions (SAR) to Hymenoptera stings is approximately 3-7% in the Northern Hemisphere. About 25% of SAR are severe (anaphylactic shock). Fatal sting reactions are very rare. The most important risk factor for severe insect sting anaphylaxis is mast cell disease. Other risk factors are higher age, vespid venom allergy (in contrast to honeybee venom allergy), repeated stings, male sex, and treatment with ACE inhibitors. Preceding large local reactions seem not to play a risk factor for subsequent SAR. SUMMARY: The majority of risk factors for severe anaphylaxis are not modifiable. For patients presenting with well defined risk factors for a very severe or even fatal anaphylaxis, VIT is of utmost importance, and they should be performed for the rest of their life. Sting challenge tests are required to identify patients in whom treatment was ineffective. Those patients, who did not receive VIT although presenting with a firm indication, or in whom VIT was stopped, require yearly monitoring to teach preventive measures and to renew the emergency kit.

Hymenoptera venom allergy among children in Italy: time for pediatricians to take action.

Hymenoptera venom allergy (HVA) is one of the most frequent causes of anaphylaxis following a bee, vespid or ant sting. Real-life data regarding the management of HVA in children are lacking. To address this unmet need, we carried out a survey defining the current management of HVA in children among pediatric allergists in Italy. Educational investments on the improvement of the management of pediatric patients with HVA are urgently needed, and our analysis represents a relevant instrument in targeting a roadmap with this aim. The time for pediatric allergists to take action has come, and a task force from the Rare Allergic Diseases Commission of the Italian Society of Pediatric Allergy and Immunology is working on the topic to improve pediatricians' knowledge and optimize the care of these patients.

Sex Differences in Adults with Insect Venom Allergy regarding Psychological Distress, Attitudes toward the Emergency Medication, and Factual Knowledge about the Disease.

BACKGROUND: Hymenoptera venom allergy (HVA) has a prevalence of 3% in adults. Although patients have no ongoing symptoms, they often suffer from an impairment of their psychological well-being and quality of life. OBJECTIVE: The aim of this study was to analyze sex-specific differences regarding the psychological burden caused by this allergy and handling of the emergency medication. METHOD: Study participants filled out a questionnaire including sociodemographic and disease-specific characteristics, the Hospital Anxiety and Depression Score (HADS), and theoretical knowledge about the emergency medication set (EMS). Additionally, an objective structured clinical examination was used to assess practical knowledge and handling of the EMS. RESULTS: Fifty-six patients were included (55.4% females). Female patients showed higher subjective anxiety levels due to HVA compared to men (mean 7.2 vs. 4.6, p = 0.0003). Furthermore, the HADS revealed that women had a significant higher anxiety level, especially after Mueller grade I-II anaphylactic reactions (mean 6.3 vs. 2.8, p = 0.0134). This was associated with a higher theoretical but not practical knowledge about their disease. On the other hand, males were less inclined to carry the emergency medication "always" or "almost always" (56 vs. 87.1%, p = 0.0015) but showed higher self-assurance in using it (mean 7.3 vs. 6.1, p = 0.0446). CONCLUSIONS: This clinical study provides evidence for sex differences in coping with HVA. The results suggest that females should be monitored more closely for allergy-associated anxiety symptoms, while men need more encouragement to carry the emergency medication.

Shedding Light on the Venom Proteomes of the Allergy-Relevant Hymenoptera Polistes dominula (European Paper Wasp) and Vespula spp. (Yellow Jacket).

Allergic reactions to stings of Hymenoptera species can have serious or even fatal consequences. If the identification of the culprit insect is possible, venom-specific immunotherapy effectively cures Hymenoptera venom allergies. Although component-resolved diagnostics has strongly evolved in recent years, the differentiation between allergies to closely related species such as Polistes dominula and Vespula spp. is still challenging. In order to generate the basis for new diagnostic and therapeutic strategies, this study aims at resolving the venom proteomes (venomes) of these species. The venoms of P. dominula and Vespula spp. (V. germanica, V. vulgaris) were analyzed by liquid chromatography-mass spectrometry. Resulting proteins were characterized regarding their function, localization and biochemical properties. The analyses yielded 157 proteins in Vespula spp. and 100 in P. dominula venom; 48 proteins, including annotated allergens, were found in both samples. In addition to a variety of venom trace molecules, new allergen candidates such as icarapin-like protein and phospholipase A2 were identified. This study elucidates the venomes of closely related allergy-eliciting Hymenoptera species. The data indicates that relying on marker allergens to differentiate between P. dominula and Vespula spp. venom allergy is probably insufficient and that strategies using cross-reactive major allergens could be more promising.

Outdated allergens are similar to unexpired extracts for the detection of allergen sensitization.

Background: Allergen extracts have relatively short shelf lives, which limits their use and increase financial loss and waste on unused extracts. It is thus important to determine if efficacy persists beyond the expiration date. Objective: To determine the in vivo efficacy and bioavailability of outdated allergen extracts for diagnosis of allergic sensitizations. Methods: We enrolled 34 participants with allergic rhinitis and 5 participants with Hymenoptera hypersensitivity. After confirming allergen sensitization with the unexpired extracts, each participant had a second skin test with the matched outdated one (up to 7 years after the expiration date). All pairs of extracts were from the same company, stored under identical conditions, and tested for microbiologic contamination. The results of 356 skin-prick tests between expired and 111 unexpired extracts were compared. Results: None of the extracts had bacterial or fungal contamination. All outdated extracts produced a positive wheal reaction, with an average of 9.4 mm, which was not significantly different than the unexpired allergens. Seven years outdated lyophilized Hymenoptera extracts showed no significant differences in the wheal's size for the intradermal test at 1 µg/mL, between 5 and 9 mm. Conclusion: Outdated allergen extracts were safe and did not seem to differ in potency and bioavailability from unexpired extracts for the detection of allergen sensitization by skin-prick testing. These results supported our hypothesis that allergen extracts have efficacy and bioavailability that extend beyond the expiry date provided by the manufacturer. For the diagnosis of aeroallergens and Hymenoptera sensitization, it seemed that allergens can be used beyond the expiration date.

Anaphylaxis in an emergency department: a retrospective 10-year study in a tertiary hospital.

Summary: Background. Anaphylaxis is a potentially fatal medical emergency. The frequency of hospital admissions for anaphylaxis seems to be increasing in the recent decades. Objective. Characterize the patients admitted for anaphylaxis to the adult emergency department (ED) of a tertiary care hospital over a 10-year period, discriminating aetiologies, clinical features and therapy administered. Methods. Retrospective, descriptive and inferential study, evaluating age, sex, Manchester triage system, suspected allergen, site of allergen exposure, comorbidities, cofactors, clinical findings and symptoms, treatment and management. Patients admitted between January 2007 and December 2016 were included. Results. Forty-three patients were enrolled: 23 males, mean age 54.3 ± 16.2 years, n = 22 had history of allergic disease. Two patients were triaged as non-urgent. The most frequently suspected causes of anaphylaxis were: drugs (33%, n = 14), Hymenoptera venoms (23%, n = 10), foods (21%, n = 9) and iodinated contrast products (12%, n = 5). Adrenaline was used in 88% of the episodes (n = 38), 55% of which (n = 21) intramuscularly. Mortality was registered in one case. At discharge, adrenaline auto-injector was prescribed in 7% (n = 3) of the patients, and Allergy and Clinical Immunology consultation (ACIC) was requested in 65% of the episodes (n = 28). Statistically significant associations (p minor 0.05) were established: a, anaphylaxis to drugs associated with a low intramuscular adrenaline use and with frequent oxygen therapy; b, anaphylaxis to food associated with intramuscular adrenaline administration; c, anaphylaxis to Hymenoptera venom associated with male sex; and d, anaphylaxis to iodinated contrasts associated with referral to ACIC and with shock. All obese patients developed shock. Conclusions. Anaphylaxis is a life-threatening condition that requires early recognition. Although most patients received adrenaline, administration was not always performed by the recommended route and only a few patients were prescribed adrenaline auto-injector.

Safety and Effectiveness of a 3-Day Rush Insect Venom Immunotherapy Protocol.

BACKGROUND: Venom immunotherapy (VIT) is an established and effective treatment for patients with Hymenoptera venom allergies. Especially during the build-up of VIT, systemic allergic reactions are a key issue. OBJECTIVE: To investigate the safety and effectiveness of a 3-day rush insect VIT protocol and a strategy for the management of individuals with VIT-induced anaphylaxis. METHODS: In this retrospective monocentric study, 11-year data regarding build-up cycles of VIT were retrieved from institutional records. The following parameters of VIT-induced anaphylaxis were analyzed: frequency, severity, time of occurrence within the build-up cycle, and impact on the success of VIT. The effectiveness of VIT was assessed by the results of sting challenges (SCs) by the culprit insect. RESULTS: In total, 1,317 initial build-up cycles of VIT were evaluated in this study, and the frequency of VIT-induced anaphylaxis was 6.6%. Anaphylaxis occurred most frequently when the daily cumulative venom dose was ≥100 µg. A group (n = 65) of patients with VIT-induced anaphylaxis in this dose range temporarily received a reduced maintenance dose, and without additional co-medications or complications, the target dose was reached after a second build-up in 91% of the cycles. After completing the VIT build-up, SCs were performed in 76.9% of the cohort, and the effectiveness of VIT was confirmed by 98.5% of the tests. CONCLUSIONS: In this study, we report a 3-day VIT rush protocol with a reasonable rate of VIT-induced anaphylaxis and excellent effectiveness of VIT.

Stinging Insect Allergens.

Hymenoptera venom allergy is one of the common causes of anaphylaxis. However, when physicians make the diagnosis of Hymenoptera venom allergy, the history of being stung is not always consistent with the results of venom-specific IgE. With the development of component-resolved diagnosis, it is possible to accurately localize an allergic reaction to certain sensitized proteins. This paper reviewed the studies that have addressed the identified allergenicity and cross-reactivity of Hymenoptera venom allergens accepted by the WHO/IUIS Nomenclature Sub-committee, the componentresolved diagnosis of Hymenoptera venom allergy and its predictive values for the efficacy and safety of venom immunotherapy. Also special attention was paid to the spread of Hymenoptera venom allergy in Asian countries.

Clinical aspects of hymenoptera venom allergy and venom immunotherapy.

Summary: Hymenoptera venom allergy (HVA) is the most frequent cause of anaphylaxis in Europe, accounting for most of the severe reactions occurring in adults, and being the second cause of anaphylaxis in children. Prevention of further episodes in patients who developed a systemic reaction (SR) is based on the correct management of the allergic emergency, the referral to an allergist for a correct diagnosis, prescription of adrenaline auto-injectors (AAI) and specific venom immunotherapy (VIT), if recommended. Diagnosis is based on the classification of the type of reaction, confirmation of an IgE-mediated pathogenesis and the identification of the offending insect. The use of component resolved diagnostics may be helpful in case of poly-sensitization or negative allergy tests with a proven history of previous SRs. When a severe SR occurs, baseline serum tryptase levels should always be assessed. The prescription of AAI is recommended or suggested for untreated patients, patients undergoing VIT and after discontinuation of treatment, according to multiple evidence. VIT is the most effective treatment available for HVA patients, as confirmed by recent European guidelines. VIT has an early, sustained and persistent protective effect and modifies the natural course of the disease. Moreover, VIT proved to be safe and well tolerated. According to a recent systematic review, no treatment-related fatalities were recorded to date. Compared to AAI, VIT significantly improves the quality of life of HVA patients by reducing the anxiety and limitations in daily activities caused by the fear of stinging insects. The memory of a life-threatening experience is the most likely reason why adherence to VIT is higher compared to immunotherapy with inhalant allergens. Several risk factors in HVA have been identified that can influence not only the severity of sting reactions in untreated patents, but also the occurrence of side effects, treatment effectiveness and the risk of relapse after discontinuation of VIT. Patient and treatment-related risk factors must be considered while selecting the best candidates for VIT, the type and duration of treatment. In this paper we address the most important issues related to HVA and VIT that may have an impact on daily clinical practice.