Oral immunotherapy for treatment of egg allergy in children

Molecular and cellular mechanisms of food allergy and food tolerance

Ingestion of innocuous antigens, including food proteins, normally results in local and systemic immune nonresponsiveness in a process termed oral tolerance. Oral tolerance to food proteins is likely to be intimately linked to mechanisms that are responsible for gastrointestinal tolerance to large numbers of commensal microbes. Here we review our current understanding of the immune mechanisms responsible for oral tolerance and how perturbations in these mechanisms might promote the loss of oral tolerance and development of food allergies. Roles for the commensal microbiome in promoting oral tolerance and the association of intestinal dysbiosis with food allergy are discussed. Growing evidence supports cutaneous sensitization to food antigens as one possible mechanism leading to the failure to develop or loss of oral tolerance. A goal of immunotherapy for food allergies is to induce sustained desensitization or even true long-term oral tolerance to food allergens through mechanisms that might in part overlap with those associated with the development of natural oral tolerance.

Local Side Effects of Sublingual and Oral Immunotherapy

Sublingual immunotherapy (SLIT) is increasingly used worldwide, and several products have been recently registered as drugs for respiratory allergy by the European Medicine Agency and the Food and Drug Administration. Concerning inhalant allergens, the safety of SLIT is overall superior to that of subcutaneous immunotherapy in terms of systemic adverse events. No fatality has been ever reported, and episodes of anaphylaxis were described only exceptionally. Looking at the historical and recent trials, most (>90%) adverse events are "local" and confined to the site of administration. For this reason, a specific grading system has been developed by the World Allergy Organization to classify and describe local adverse events. There is an increasing amount of literature concerning oral desensitization for food allergens, referred to as oral immunotherapy. Also, in this case, local side effects are predominant, although systemic adverse events are more frequent than with inhalant allergens. We review herein the description of local side effects due to SLIT, with a special focus on large trials having a declared sample size calculation. The use of the Medical Dictionary for Regulatory Activities nomenclature for adverse events is mentioned in this context, as recommended by regulatory agencies. It is expected that a uniform classification/grading of local adverse events will improve and harmonize the surveillance and reporting on the safety of SLIT.

Early oral immunotherapy in peanut-allergic preschool children is safe and highly effective

BACKGROUND

Oral immunotherapy (OIT) is an effective experimental food allergy treatment that is limited by treatment withdrawal and the frequent reversibility of desensitization if interrupted. Newly diagnosed preschool children may have clinical and immunological characteristics more amenable to treatment.

OBJECTIVE

We sought to test the safety, effectiveness, and feasibility of early OIT (E-OIT) in the treatment of peanut allergy.

METHODS

We enrolled 40 children aged 9 to 36 months with suspected or known peanut allergy. Qualifying subjects reacted to peanut during an entry food challenge and were block-randomized 1:1 to receive E-OIT at goal maintenance doses of 300 or 3000 mg/d in a double-blinded fashion. The primary end point, sustained unresponsiveness at 4 weeks after stopping early intervention oral immunotherapy (4-SU), was assessed by double-blinded, placebo-controlled food challenge either upon achieving 4 prespecified criteria, or after 3 maintenance years. Peanut-specific immune responses were serially analyzed. Outcomes were compared with 154 matched standard-care controls.

RESULTS

Of 40 consented subjects, 3 (7.5%) did not qualify. Overall, 29 of 37 (78%) in the intent-to-treat analysis achieved 4-SU (300-mg arm, 17 of 20 [85%]; 3000 mg, 12 of 17 [71%], P = .43) over a median of 29 months. Per-protocol, the overall proportion achieving 4-SU was 29 of 32 (91%). Peanut-specific IgE levels significantly declined in E-OIT-treated children, who were 19 times more likely to successfully consume dietary peanut than matched standard-care controls, in whom peanut-specific IgE levels significantly increased (relative risk, 19.42; 95% CI, 8.7-43.7; P < .001). Allergic side effects during E-OIT were common but all were mild to moderate.

CONCLUSIONS

At both doses tested, E-OIT had an acceptable safety profile and was highly successful in rapidly suppressing allergic immune responses and achieving safe dietary reintroduction.

Current and Emerging Therapies for IgE-Mediated Food Allergy

Food allergies are a growing clinical problem leading to increased health care utilization and decreases in patient quality of life. Current treatment recommendations include strict dietary avoidance of the offending food as well as use of self-injectable epinephrine in case of accidental exposure with allergic reaction. Although many individuals will eventually outgrow their food allergies, a substantial number will not. Significant effort has been made to find novel treatments that protect patients from food-triggered reactions as well as to develop immune-modulating therapies that could lead to tolerance. In this review, three therapies that have shown the most promise for the treatment of food allergies are highlighted: oral immunotherapy, sublingual immunotherapy, and epicutaneous immunotherapy.

Development of a prediction model of severe reaction in boiled egg challenges

BACKGROUND

We have proposed a new scoring system (Anaphylaxis SCoring Aichi: ASCA) for a quantitative evaluation of the anaphylactic reaction that is observed in an oral food challenge (OFC). Furthermore, the TS/Pro (Total Score of ASCA/cumulative protein dose) can be a marker to represent the overall severity of a food allergy. We aimed to develop a prediction model for a severe allergic reaction that is provoked in a boiled egg white challenge.

METHODS

We used two separate datasets to develop and validate the prediction model, respectively. The development dataset included 198 OFCs, that tested positive. The validation dataset prospectively included 140 consecutive OFCs, irrespective of the result. A 'severe reaction' was defined as a TS/Pro higher than 31 (the median score of the development dataset). A multivariate logistic regression analysis was performed to identify the factors associated with a severe reaction and develop the prediction model.

RESULTS

The following four factors were independently associated with a severe reaction: ovomucoid specific IgE class (OM-sIgE: 0-6), aged 5 years or over, a complete avoidance of egg, and a total IgE < 1000 IU/mL. Based on these factors, we made a simple scoring prediction model. The model showed good discrimination in a receiver operating characteristic analysis; area under the curve (AUC) = 0.84 in development dataset, AUC = 0.85 in validation dataset. The prediction model significantly improved the AUC in both datasets compared to OM-sIgE alone.

CONCLUSIONS

This simple scoring prediction model was useful for avoiding risky OFC.

[Allergen-specific immunotherapy for food allergies in childhood. Current options and future perspectives]

During recent years increasing research has been conducted on casual treatment options for food allergy, with focus on oral immunotherapy (OIT) for hen's egg, cow's milk and peanut allergy. Several studies could show that OIT leads to desensitization or an increase of threshold. However, severe adverse events during this treatment are not uncommon. Whether OIT leads to a sustained, 'robust' development of tolerance in patients has not yet been thoroughly investigated. Besides OIT, some studies on sublingual (SLIT) and epicutaneous immunotherapy (EPIT) were performed, aiming to improve the safety profile. Furthermore, there are some pilot studies investigating a combined treatment of SLIT and OIT or a combined use of anti-IgE treatment or probiotic supplementation with OIT. Further placebo-controlled trials with larger sample size are needed in order to develop standardized protocols before immunotherapy may be used as a therapeutic option for food allergy outside of clinical trials.

Understanding probiotics' role in allergic children: the clue of gut microbiota profiling

PURPOSE OF REVIEW

To investigate the functional role of gut microbiota in diet-modulated diseases, evaluating probiotic administration effects by systems biology-driven approaches. Understanding the role of host-gut microbial and gut microbe-microbe interactions in either allergic and healthy children may assist in selecting effective and targeted probiotics for personalized therapies.

RECENT FINDINGS

Food allergy shows a significant increase, especially in Western countries where growing epidemiological data indicate prevalence of small family groups, limited rate of infections in childhood compared with low-income countries, high consumption of sterile foods, hence stimulating a poor trigger of the gut immune system. Therefore, new therapeutic strategies to treat food allergy consist of probiotic administration since early life, thus modulating gut microbiota through immune system stimulation at the mucosal level.

SUMMARY

Currently, new insights for probiotic selection should take into consideration both phenotyping and genotyping bacterial features and host-microbial cross-talk at gut level, by employing multicomponent systems biology approaches to unveil gut ecosystem dynamics in terms of bacteria phylotypes and their metabolic activities. Moreover, new food processes need to be considered to assess the actual performance of probiotic strains administered to allergic patients. The advent of high-performance platforms employing genomic- and mass spectrometry-based techniques has opened new perspectives on the gut microbiota field, and may now serve as advanced tool to dynamically investigate the interplay between probiotics and gut microbiota ecology under allergic conditions.

Epicutaneous immunotherapy induces gastrointestinal LAP+ regulatory T cells and prevents food-induced anaphylaxis

BACKGROUND

The attempt to induce oral tolerance as a treatment for food allergy has been hampered by a lack of sustained clinical protection. Immunotherapy by nonoral routes, such as the skin, may be more effective for the development of maintained tolerance to food allergens.

OBJECTIVE

We sought to determine the efficacy and mechanism of tolerance induced by epicutaneous immunotherapy (EPIT) in a model of food-induced anaphylaxis.

METHODS

C3H/HeJ mice were sensitized to ovalbumin (OVA) orally or through the skin and treated with EPIT using OVA-Viaskin patches or oral immunotherapy using OVA. Mice were orally challenged with OVA to induce anaphylaxis. Antigen-specific regulatory T (Treg)-cell induction was assessed by flow cytometry using a transgenic T-cell transfer model.

RESULTS

By using an adjuvant-free model of food allergy generated by epicutaneous sensitization and reactions triggered by oral allergen challenge, we found that EPIT induced sustained protection against anaphylaxis. We show that the gastrointestinal tract is deficient in de novo generation of Treg cells in allergic mice. This defect was tissue-specific, and epicutaneous application of antigen generated a population of gastrointestinal-homing LAP⁺Foxp3^- Treg cells. The mechanism of protection was found to be a novel pathway of direct TGF-β-dependent Treg-cell suppression of mast cell activation, in the absence of modulation of T- or B-cell responses.

CONCLUSIONS

Our data highlight the immune communication between skin and gastrointestinal tract, and identifies novel mechanisms by which epicutaneous tolerance can suppress food-induced anaphylaxis.

Post-sensitization administration of non-digestible oligosaccharides and Bifidobacterium breve M-16V reduces allergic symptoms in mice

To support dietary management of severe cow's milk allergic infants, a synbiotic mixture of non-digestible oligosaccharides and Bifidobacterium breve M-16V (B. breve) was designed from source materials that are completely cow's milk-free. It was investigated whether this specific synbiotic concept can reduce an established food allergic response in a research model for hen's egg allergy. Mice were orally sensitized once a week for 5 weeks to ovalbumin (OVA) using cholera toxin (CT) as an adjuvant. Non-sensitized mice received CT in PBS only. Sensitized mice were fed a control diet or a diet enriched with short-chain- (scFOS) and long-chain fructo-oligosaccharides (lcFOS), B. breve or scFOSlcFOS + B. breve for 3 weeks starting after the last sensitization. Non-sensitized mice received the control diet. Anaphylactic shock symptoms, acute allergic skin responses and serum specific IgE, mMCP-1 and galectin-9 were measured upon OVA challenge. Activated Th2-, Th1-cells and regulatory T-cells were quantified in spleen and mesenteric lymph nodes (MLN) and cytokine profiles were analyzed. Short chain fatty acids (SCFA) were measured in ceacal samples. The acute allergic skin response was reduced in mice fed the scFOSlcFOS + B. breve diet compared to mice fed any of the other diets. A reduction in mast cell degranulation (mMCP-1) and anaphylactic shock symptoms was also observed in these mice. Unstimulated splenocyte cultures produced increased levels of IL10 and IFNg in mice fed the scFOSlcFOS + B. breve diet. Correspondingly, increased percentages of activated Th1 cells were observed in the spleen. Allergen-specific re-stimulation of splenocytes showed a decrease in IL5 production. In summary; post-sensitization administration of scFOSlcFOS + B. breve was effective in reducing allergic symptoms after allergen challenge. These effects coincided with changes in regulatory and effector T-cell subsets and increases in the SCFA propionic acid. These results suggest immune modulatory benefits of dietary intervention with a unique combination of scFOSlcFOS + B. breve in established food allergy. Whether these effects translate to human applications is subject for ongoing clinical studies.

Food specific oral immunotherapy: a potential treatment for food allergy

Food allergy is a potentially life-threatening condition affecting up to 8% of children and up to 2% of adults in westernized countries. There are currently no approved treatments for food allergy apart from avoidance. The apparent increase in incidence of food allergies over the past few decades calls attention to the need for effective, disease-modifying therapies for food allergies. Oral immunotherapy (OIT) is a promising experimental treatment in which food allergic patients consume increasing quantities of food in attempt to increase their threshold for allergic reaction. Studies are ongoing to determine whether OIT is capable of safely inducing not only desensitization but also tolerance to the allergenic foods. This article focuses on recent relevant studies of OIT for the treatment of common food allergies.

Assessing the efficacy of oral immunotherapy for the desensitisation of peanut allergy in children (STOP II): a phase 2 randomised controlled trial: a critical appraisal

AIM

Anagnostou et al. investigated the efficacy of oral immunotherapy (OIT) in treating peanut allergy.

SETTING AND DESIGN

An unmasked randomized controlled crossover trial of 7-16 year olds with double-blind placebo-controlled food challenge (DBPCFC)-proven peanut allergy. The first phase compared an active group undergoing 26 weeks of OIT with daily ingestion of peanut protein vs. a control group avoiding peanuts. Both groups underwent DBPCFC to peanut at 26 weeks. In the second phase the control group was then offered OIT for 26 weeks.

STUDY EXPOSURE

Participants undergoing OIT attended hospital every 2 weeks to initiate and increase their daily peanut protein dose through nine stages (2, 5, 12·5, 25, 50, 100, 200, 400 and 800 mg - about five peanuts), subsequently maintaining consumption at the highest tolerated dose. Primary outcome The primary outcome compared the proportions of active- and control-group participants able to ingest a cumulative dose of 1400 mg of peanut protein (about 10 peanuts) during their DBPCFC at the end of the first phase without reacting. Secondary outcomes Further outcomes included the proportion of participants who tolerated the top maintenance dosage of 800 mg protein up to 26 weeks; the proportion of the control group who were desensitized or tolerated daily ingestion of 800 mg protein in the second phase; threshold changes in no observed adverse effect level after OIT (NOAEL: defined as the highest dose of peanut protein tolerated in milligrams of protein during challenge or immunotherapy); change in quality of life; number and type of adverse events; and immunological parameters (basophil reactivity, peanut-specific IgE, total IgE and skin-prick test).

RESULTS

Primary outcome Twenty-four of 39 (62%) of the active group were able to tolerate the 1400 mg of peanut protein during their DBPCFC after 26 weeks of OIT, compared with none of the 46 control participants (P < 0·001). Secondary outcomes Twenty-five of 46 (54%) of the control group had a negative 1400-mg peanut protein challenge at the end of phase 2. Combining the two groups, 49 of 85 children (58%) were desensitized. Thirty-three of 39 (85%) active participants in phase one and 42 of 46 (91%) control participants in phase two tolerated 800 mg of OIT daily - a combined result of 75 of 85 (88%) trial participants. The median absolute change in NOAEL between baseline and 26 weeks was 1345 mg (P = 0·002), or a 25·5-fold increase (P < 0·001) for the active group. Both the active and control groups demonstrated a significant improvement (decrease) in Food Allergy Quality of Life scores after OIT in the under-13-year-old participants: -1·61 and -1·41, respectively (both P < 0·001). Mild side-effects predominated, with 54 (57%) reporting abdominal pain and 31 (33%) reporting vomiting. However, 21 (22%) also reported wheezing and one (1%) laryngeal oedema. One participant received adrenaline by self-administration on two occasions for wheezing.

CONCLUSIONS

Anagnostou et al. concluded that OIT successfully induced desensitization in challenge-proven peanut-allergic children and resulted in a clinically and socially meaningful increase in tolerated peanut protein. Quality of life improved after intervention and there was a good safety profile.

Hydrolysed egg displays strong decrease in allergenicity and is well tolerated by egg-allergic patients

Food allergies are believed to be on the rise, and currently, management relies on the avoidance of the food. Hen's egg allergy is after cow's milk allergy the most common food allergy; eggs are used in many food products and thus difficult to avoid. A technological process using a combination of enzymatic hydrolysis and heat treatment was designed to produce modified hen's egg with reduced allergenic potential. Biochemical (SDS-PAGE, Size exclusion chromatography and LC-MS/MS) and immunological (ELISA, immunoblot, RBL-assays, animal model) analysis showed a clear decrease in intact proteins as well as a strong decrease of allergenicity. In a clinical study, 22 of the 24 patients with a confirmed egg allergy who underwent a double-blind food challenge with the hydrolysed egg remained completely free of symptoms. Hydrolysed egg products may be beneficial as low-allergenic foods for egg-allergic patients to extent their diet.

Patient quality of life following induction of oral immunotherapy for food allergy

BACKGROUND

Patient quality of life improves following successful completion of oral immunotherapy (OIT), but the process itself might have undesirable effects. We aimed to evaluate patient quality of life following OIT initial induction.

METHODS

The Hebrew version of the Food Allergy Quality of Life Questionnaire-Parental Form (FAQLQ-PF) was validated and administered to the parents of children following the first week of OIT for food allergy (n = 119). Patient demographics and clinical history as well as the course of initial induction week were reviewed.

RESULTS

Pre-OIT severity of food allergy, defined as severity of reactions due to accidental exposure to the allergenic food (anaphylactic reactions, p = 0.017; epinephrine use, p = 0.049; emergency room referrals p = 0.003; and hospital admissions, p = 0.015) and a lower number of tolerated doses during initial induction, reflective of a lower maximal tolerated dose for the different allergens (p = 0.011) were associated with worse total FAQLQ-PF scores. The number of tolerated doses during induction and pre-OIT emergency room referrals remained significantly associated with worse total score of the FAQLQ-PF on multivariate analysis (p = 0.016 and p = 0.005, respectively). The correlation between the number of tolerated doses and quality of life scores was moderate-strong primarily in children aged 6-12 years (Total score, r = -0.41, p = 0.001; Emotional Impact r = -0.42, p = 0.001; Food Anxiety, r = -0.38, p = 0.002; Social and Dietary Limitations, r = -0.33, p = 0.009).

CONCLUSIONS

Pre-OIT reaction severity affects quality of life in both preschool and school-aged food-allergic children. In contrast, a lower maximal tolerated dose during OIT induction is associated with worse indices of quality of life primarily in children aged 6-12 years.

EAACI Molecular Allergology User's Guide

The availability of allergen molecules ('components') from several protein families has advanced our understanding of immunoglobulin E (IgE)-mediated responses and enabled 'component-resolved diagnosis' (CRD). The European Academy of Allergy and Clinical Immunology (EAACI) Molecular Allergology User's Guide (MAUG) provides comprehensive information on important allergens and describes the diagnostic options using CRD. Part A of the EAACI MAUG introduces allergen molecules, families, composition of extracts, databases, and diagnostic IgE, skin, and basophil tests. Singleplex and multiplex IgE assays with components improve both sensitivity for low-abundance allergens and analytical specificity; IgE to individual allergens can yield information on clinical risks and distinguish cross-reactivity from true primary sensitization. Part B discusses the clinical and molecular aspects of IgE-mediated allergies to foods (including nuts, seeds, legumes, fruits, vegetables, cereal grains, milk, egg, meat, fish, and shellfish), inhalants (pollen, mold spores, mites, and animal dander), and Hymenoptera venom. Diagnostic algorithms and short case histories provide useful information for the clinical workup of allergic individuals targeted for CRD. Part C covers protein families containing ubiquitous, highly cross-reactive panallergens from plant (lipid transfer proteins, polcalcins, PR-10, profilins) and animal sources (lipocalins, parvalbumins, serum albumins, tropomyosins) and explains their diagnostic and clinical utility. Part D lists 100 important allergen molecules. In conclusion, IgE-mediated reactions and allergic diseases, including allergic rhinoconjunctivitis, asthma, food reactions, and insect sting reactions, are discussed from a novel molecular perspective. The EAACI MAUG documents the rapid progression of molecular allergology from basic research to its integration into clinical practice, a quantum leap in the management of allergic patients.

Differential response in allergen-specific IgE, IgGs, and IgA levels for predicting outcome of oral immunotherapy

BACKGROUND

Oral immunotherapy (OIT) induces desensitization and/or tolerance in patients with persistent food allergy, but the biomarkers of clinical outcomes remain obscure. Although OIT-induced changes in serum allergen-specific IgE and IgG4 levels have been investigated, the response of other allergen-specific IgG subclasses and IgA during OIT remains obscure.

METHODS

A pilot study was conducted to investigate egg OIT-induced changes in allergen-specific IgE, IgG subclasses, and IgA levels and search for possible prediction biomarkers of desensitization. We measured serum levels of egg white-, ovomucoid-, and ovalbumin-specific IgE, IgA, and IgG subclasses by high-sensitivity allergen microarray in 26 children with egg allergy who received rush OIT.

RESULTS

Allergen-specific IgE gradually decreased while IgG4 increased during 12-month OIT. Serum levels of IgG1, IgG3, and IgA increased significantly after the rush phase, then decreased during the maintenance phase. IgG2 levels changed in a manner similar to that of IgG4. In particular, significantly high fold increases in egg white-specific IgG1, relative to baseline, after the rush phase and high IgA levels before OIT were observed in responders, compared with low-responders to OIT. Patients who could not keep desensitization showed relatively small changes in all immunoglobulin levels during OIT.

CONCLUSION

The response to OIT was associated with significant increases in serum allergen-specific IgG1 levels after rush phase and high baseline IgA levels, compared with small changes in immunoglobulin response in low-responders. The characteristic IgG1 changes and IgA levels in the responders could be potentially useful biomarkers for the prediction of positive clinical response to OIT.

The rise of food allergy: Environmental factors and emerging treatments

Food allergy has rapidly increased in prevalence, suggesting an important role for environmental factors in disease susceptibility. The immune response of food allergy is characterized by IgE production, and new findings from mouse and human studies indicate an important role of the cytokine IL-9, which is derived from both T cells and mast cells, in disease manifestations. Emerging evidence suggests that route of exposure to food, particularly peanut, is important. Exposure through the skin promotes sensitization while early exposure through the gastrointestinal tract promotes tolerance. Evidence from mouse studies indicate a role of the microbiome in development of food allergy, which is supported by correlative human studies showing a dysbiosis in food allergy. There is no approved treatment for food allergy, but emerging therapies are focused on allergen immunotherapy to provide desensitization, while pre-clinical studies are focused on using adjuvants or novel delivery approaches to improve efficacy and safety of immunotherapy.

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Emerging evidence suggests that route of exposure to food allergens in early life determines sensitization versus tolerance.

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The microbiota and dietary factors appear to play a key role in susceptibility to food allergy.

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Immunotherapy applied via different routes is currently the most promising form of experimental treatment for food allergy.

Effect of Avoidance on Peanut Allergy after Early Peanut Consumption

BACKGROUND

In a randomized trial, the early introduction of peanuts in infants at high risk for allergy was shown to prevent peanut allergy. In this follow-up study, we investigated whether the rate of peanut allergy remained low after 12 months of peanut avoidance among participants who had consumed peanuts during the primary trial (peanut-consumption group), as compared with those who had avoided peanuts (peanut-avoidance group).

METHODS

At the end of the primary trial, we instructed all the participants to avoid peanuts for 12 months. The primary outcome was the percentage of participants with peanut allergy at the end of the 12-month period, when the participants were 72 months of age.

RESULTS

We enrolled 556 of 628 eligible participants (88.5%) from the primary trial; 550 participants (98.9%) had complete primary-outcome data. The rate of adherence to avoidance in the follow-up study was high (90.4% in the peanut-avoidance group and 69.3% in the peanut-consumption group). Peanut allergy at 72 months was significantly more prevalent among participants in the peanut-avoidance group than among those in the peanut-consumption group (18.6% [52 of 280 participants] vs. 4.8% [13 of 270], P<0.001). Three new cases of allergy developed in each group, but after 12 months of avoidance there was no significant increase in the prevalence of allergy among participants in the consumption group (3.6% [10 of 274 participants] at 60 months and 4.8% [13 of 270] at 72 months, P=0.25). Fewer participants in the peanut-consumption group than in the peanut-avoidance group had high levels of Ara h2 (a component of peanut protein)-specific IgE and peanut-specific IgE; in addition, participants in the peanut-consumption group continued to have a higher level of peanut-specific IgG4 and a higher peanut-specific IgG4:IgE ratio.

CONCLUSIONS

Among children at high risk for allergy in whom peanuts had been introduced in the first year of life and continued until 5 years of age, a 12-month period of peanut avoidance was not associated with an increase in the prevalence of peanut allergy. Longer-term effects are not known. (Funded by the National Institute of Allergy and Infectious Diseases and others; LEAP-On ClinicalTrials.gov number, NCT01366846.).

Basophil activation test: food challenge in a test tube or specialist research tool?

Oral food challenge (OFC) is the gold-standard to diagnose food allergy; however, it is a labour and resource-intensive procedure with the risk of causing an acute allergic reaction, which is potentially severe. Therefore, OFC are reserved for cases where the clinical history and the results of skin prick test and/or specific IgE do not confirm or exclude the diagnosis of food allergy. This is a significant proportion of patients seen in Allergy clinics and results in a high demand for OFC. The basophil activation test (BAT) has emerged as a new diagnostic test for food allergy. With high diagnostic accuracy, it can be particularly helpful in the cases where skin prick test and specific IgE are equivocal and may allow reducing the need for OFC. BAT has high specificity, which confers a high degree of certainty in confirming the diagnosis of food allergy and allows deferring the performance of OFC in patients with a positive BAT. The diagnostic utility of BAT is allergen-specific and needs to be validated for different allergens and in specific patient populations. Standardisation of the laboratory methodology and of the data analyses would help to enable a wider clinical application of BAT.

Long-term treatment with egg oral immunotherapy enhances sustained unresponsiveness that persists after cessation of therapy

BACKGROUND

We previously reported the results of a randomized placebo-controlled study of egg oral immunotherapy (eOIT) in which 27.5% of subjects achieved sustained unresponsiveness (SU) after 2 years. Here we report the results of treatment through 4 years and long-term follow-up.

OBJECTIVE

We sought to evaluate the efficacy and safety of eOIT in participants treated up to 4 years.

METHODS

Children with egg allergy (5-18 years old) received eOIT (n = 40) for up to 4 years or placebo (n = 15) for 1 year or less. The key outcome was the percentage of subjects achieving SU by year 4. Safety and immunologic assessments were performed, and long-term follow-up questionnaires (LFQs) were administered after study conclusion (LFQ-1) and 1 year later (LFQ-2).

RESULTS

Of 40 eOIT-treated subjects, 20 (50.0%) of 40 demonstrated SU by year 4. For those subjects still dosing during years 3 and 4, mild symptoms were present in 12 (54.5%) of 22 subjects. At the time of the LFQ, more subjects receiving eOIT (LFQ-1, 23/34 [68%]; LFQ-2, 21/33 [64%]) were consuming unbaked and baked egg versus placebo (LFQ-1, 2/11 [18%], P = .006; LFQ-2, 3/12 [25%], P = .04). Of subjects achieving SU, 18 (90%) of 20 completed the LFQ, with 18 (100%) of 18 reporting consumption of all forms of egg. When compared with subjects not achieving SU, subjects achieving SU had higher IgG4 values (P = .001) and lower egg skin prick test scores (P = .0002) over time and a lower median baseline ratio of egg-specific IgE to total IgE (1.1% vs 2.7%, P = .04).

CONCLUSIONS

SU after eOIT is enhanced with longer duration of therapy and increases the likelihood of tolerating unbaked egg in the diet.

Improving the safety of oral immunotherapy for food allergy

Food allergy is a major public health problem in children, impacting upon the affected individual, their families and others charged with their care, for example educational establishments, and the food industry. In contrast to most other paediatric diseases, there is no established cure: current management is based upon dietary avoidance and the provision of rescue medication in the event of accidental reactions, which are common. This strategy has significant limitations and impacts adversely on health-related quality of life. In the last decade, research into disease-modifying treatments for food allergy has emerged, predominantly for peanut, egg and cow's milk. Most studies have used the oral route (oral immunotherapy, OIT), in which increasing amounts of allergen are given over weeks-months. OIT has proven effective to induce immune modulation and 'desensitization' - that is, an increase in the amount of food allergen that can be consumed, so long as regular (typically daily) doses are continued. However, its ability to induce permanent tolerance once ongoing exposure has stopped seems limited. Additionally, the short- and long-term safety of OIT is often poorly reported, raising concerns about its implementation in routine practice. Most patients experience allergic reactions and, although generally mild, severe reactions have occurred. Long-term adherence is unclear, which rises concerns given the low rates of long-term tolerance induction. Current research focuses on improving current limitations, especially safety. Strategies include alternative routes (sublingual, epicutaneous), modified hypoallergenic products and adjuvants (anti-IgE, pre-/probiotics). Biomarkers of safe/successful OIT are also under investigation.

A practical view of immunotherapy for food allergy

Food allergy is common and sometimes life threatening for Korean children. The current standard treatment of allergen avoidance and self-injectable epinephrine does not change the natural course of food allergy. Recently, oral, sublingual, and epicutaneous immunotherapies have been studied for their effectiveness against food allergy. While various rates of desensitization (36% to 100%) and tolerance (28% to 75%) have been induced by immunotherapies for food allergy, no single established protocol has been shown to be both effective and safe. In some studies, immunologic changes after immunotherapy for food allergy have been revealed. Adverse reactions to these immunotherapies have usually been localized, but severe systemic reactions have been observed in some cases. Although immunotherapy cannot be recommended for routine practice yet, results from recent studies demonstrate that immunotherapies are promising for the treatment of food allergy.

Clinical and laboratory 2-year outcome of oral immunotherapy in patients with cow's milk allergy

Studies examining the long-term effect of oral immunotherapy in food-allergic patients are limited. We investigated cow's milk-allergic patients, >6 months after the completion of oral immunotherapy (n = 197). Questionnaires, skin prick tests, and basophil activation assays were performed. Of the 195 patients contacted, 180 (92.3%) were consuming milk protein regularly. Half experienced adverse reactions, mostly mild. Thirteen patients (6.7%) required injectable epinephrine. Higher reaction rate after immunotherapy was associated with more anaphylactic episodes before treatment and a lower starting dose (OR = 2.1, P = 0.035 and OR = 2.3, P = 0.035, respectively). Reaction rate in patients who were 6-15 months, 15-30 months, or >30 months post-treatment decreased from 0.28/month to 0.21/month to 0.15/month, respectively (P < 0.01). Milk-induced %CD63 and %CD203c expression was significantly lower in patients >24 months vs in patients <24 months post-treatment (P = 0.038 and P = 0.047, respectively). In conclusion, many patients experience mild adverse reactions after completing oral immunotherapy and some require injectable epinephrine. Progressive desensitization, both clinically and in basophil reactivity, occurs over time.

Wheat allergy: diagnosis and management

Triticum aestivum (bread wheat) is the most widely grown crop worldwide. In genetically predisposed individuals, wheat can cause specific immune responses. A food allergy to wheat is characterized by T helper type 2 activation which can result in immunoglobulin E (IgE) and non-IgE mediated reactions. IgE mediated reactions are immediate, are characterized by the presence of wheat-specific IgE antibodies, and can be life-threatening. Non-IgE mediated reactions are characterized by chronic eosinophilic and lymphocytic infiltration of the gastrointestinal tract. IgE mediated responses to wheat can be related to wheat ingestion (food allergy) or wheat inhalation (respiratory allergy). A food allergy to wheat is more common in children and can be associated with a severe reaction such as anaphylaxis and wheat-dependent, exercise-induced anaphylaxis. An inhalation induced IgE mediated wheat allergy can cause baker’s asthma or rhinitis, which are common occupational diseases in workers who have significant repetitive exposure to wheat flour, such as bakers. Non-IgE mediated food allergy reactions to wheat are mainly eosinophilic esophagitis (EoE) or eosinophilic gastritis (EG), which are both characterized by chronic eosinophilic inflammation. EG is a systemic disease, and is associated with severe inflammation that requires oral steroids to resolve. EoE is a less severe disease, which can lead to complications in feeding intolerance and fibrosis. In both EoE and EG, wheat allergy diagnosis is based on both an elimination diet preceded by a tissue biopsy obtained by esophagogastroduodenoscopy in order to show the effectiveness of the diet. Diagnosis of IgE mediated wheat allergy is based on the medical history, the detection of specific IgE to wheat, and oral food challenges. Currently, the main treatment of a wheat allergy is based on avoidance of wheat altogether. However, in the near future immunotherapy may represent a valid way to treat IgE mediated reactions to wheat.

Recent Understandings of Pet Allergies

Allergic reactions to pets have been recognized for at least a hundred years. Yet our understanding of the effects of all of the interactions between pet exposures and human immune responses continues to grow. Allergists, epidemiologists, and immunologists have spent years trying to better understand how exposures to pet allergens lead to allergic sensitization (the production of allergen-specific immunoglobulin class E [IgE] antibodies) and subsequent allergic disease. A major new development in this understanding is the recognition that pet exposures consist of not only allergen exposures but also changes in microbial exposures. Exposures to certain pet-associated microbes, especially in the neonatal period, appear to be able to dramatically alter how a child’s immune system develops and this in turn reduces the risk of allergic sensitization and disease. An exciting challenge in the next few years will be to see whether these changes can be developed into a realistic preventative strategy with the expectation of significantly reducing allergic disease, especially asthma.

Food Allergies: Novel Mechanisms and Therapeutic Perspectives

Childhood food allergy (FA) rates have rapidly increased with significant direct medical costs for the health care system and even larger costs for the families with a food-allergic child. The possible causes of food allergy become the target of intense scrutiny in recent years. Increasing evidence underline the importance in early life of gut microbiome in the development of allergic diseases. There are a range of factors in the modern environment that may be associated with changes to both the gut microbiome and risk of FA, such as mode of delivery, antibiotic exposure, infant feeding practices, farming environment, and country of origin. Knowledge of the relationship between early life gut microbiome and allergic diseases may facilitate development of novel preventive and treatment strategies. Based on our current knowledge, there are no currently available approved therapies for food allergy. More studies are needed to evaluate the safety and efficacy of allergen-specific and allergen-nonspecific approaches, as well as combination approaches.

Better management of wheat allergy using a very low-dose food challenge: A retrospective study

BACKGROUND

Low-dose reactive wheat-allergic children are at a high risk of a positive oral food challenge (OFC). The present study aimed to evaluate whether the results of a very low-dose (VL) OFC would contribute to better wheat allergy management in this population.

METHODS

We retrospectively reviewed wheat-allergic subjects who underwent a VL OFC with 2 g of udon noodles (equivalent to 53 mg of wheat protein) and had a previous allergic reaction to <15 g of udon noodles (equivalent to 400 mg of wheat protein) within 2 years before the OFC. Subjects who passed the OFC were defined as VL tolerant; those who failed were considered VL reactive. In VL tolerant subjects, the dose was increased to 15 g of udon noodles either during an OFC in our hospital or gradually at home.

RESULTS

Of the 57 included subjects (median age, 2.9 years; range, 1.0-11.8 years), 32 (56%) were VL tolerant and 25 (44%) were VL reactive. Most reactions during the OFC could be treated with an antihistamine and/or a nebulized β2 agonist. VL tolerant subjects consumed 2 g of udon noodles or a seasoning containing wheat. Within a year after the OFC, 18 VL tolerant subjects (56%), but no VL reactive subjects, were able to consume 15 g of udon noodles (p < 0.001).

CONCLUSIONS

A VL OFC can shift the management of some low-dose reactive wheat-allergic children from complete avoidance to partial wheat intake.

Management and Prevention of Anaphylaxis

Anaphylaxis prevalence has increased within the last few years. This may be due to a marked increase in allergic sensitization to foods especially in the pediatric population, as well as to an increase in outdoor recreational habits and the availability of new biologic medications.  Furthermore, guidelines for the diagnosis of anaphylaxis have been published, thus facilitating the recognition of this disorder. Diagnosis of anaphylaxis is mainly based on history and clinical criteria of organ system involvement. The serum tryptase assay is now commercially available and may be a helpful diagnostic tool in certain clinical situations involving hypotension, but not in the context of food-induced anaphylaxis. Treatment of anaphylaxis mainly involves the use of epinephrine as a first line medication for severe manifestations followed by  symptomatic management of specific  symptoms, such as antihistamines for urticaria and albuterol for wheezing. Although commonly practiced, treatment with systemic corticosteroids  is not supported by evidence-based literature. Observation in a medical facility for 4-6 hours is recommended to monitor for late phase reactions, although these rarely occur. Education is an essential component of management of a patient with a previous history of anaphylaxis, emphasizing early use of epinephrine and providing a written action plan. Referral to a board-certified allergist/immunologist is recommended to determine  the cause of the anaphylaxis as well as to rule out other potential conditions. In this review, our main focus will be on the treatment and prevention of anaphylaxis while providing our readers with a brief introduction to the diagnosis of anaphylaxis, its prevalence and its most common causes.

Recent Advances in Management of Pediatric Food Allergy

Many children now suffer with a food allergy, immunoglobulin E (IgE) and/or non-IgE mediated. Food allergies have a significant impact on the child’s quality of life, as well as that of their family, due to the resultant dietary restrictions and the constant threat of a potentially life-threatening reaction. At present, there is no cure for food allergies, but there are exciting advances occurring in the management of IgE mediated allergies, including a more active approach to management with anticipatory screening testing, early introduction of common food allergens, active tolerance induction, use of biologics and active risk management. These areas will be discussed in this review.

Current Options for the Treatment of Food Allergy

Food allergy is increasing in prevalence; as a result, there is intense focus on developing safe and effective therapies. Current methods of specific immunotherapy include oral, sublingual, and epicutaneous, while nonspecific methods that have been investigated include: Chinese herbal medicine, probiotics, and anti-IgE antibodies. Although some studies have demonstrated efficacy in inducing desensitization, questions regarding safety and the potential for achieving immune tolerance remain. Although some of these therapies demonstrate promise, further investigation is required before their incorporation into routine clinical practice.

Early sustained unresponsiveness after short-course egg oral immunotherapy: a randomized controlled study in egg-allergic children

BACKGROUND

No studies have evaluated the potential of egg oral immunotherapy (egg-OIT) to induce sustained unresponsiveness after discontinuing therapy following short-term treatments.

OBJECTIVE

We assessed the efficacy of short-course egg-OIT to induce sustained unresponsiveness.

METHODS

Sixty-one egg-allergic children, 5 to 17 years old, with positive double-blind placebo-controlled food challenge (DBPCFC) to dehydrated egg white (EW) were randomized to receive egg-OIT (OITG) for 3 months (maintenance dose one undercooked egg every 48 hours) or to continue egg avoidance diet (control group, CG) for 4 months. Children who completed egg-OIT avoided egg for 1 month. At 4 months, both groups underwent a DBPCFC. OITG participants who passed this challenge were instructed to add egg to their diet ad libitum. Immune markers were studied at different time points.

RESULTS

Ninety-three percent (28/30) of OITG children were desensitized in a median of 32.5 days (IQR, 14 days). At 4 months, 1/31 (3%) in CG passed DBPCFC and 11/30 (37%) of OITG (95% CI, 14 to 51%; P = 0.003), all of them were consuming egg at 36 months. A decrease in EW, OVA and OVM skin test results and OVA-specific IgE (sIgE) levels was observed on OITG at 4 months (P = 0.001). EW-, OVA- and OVM-sIgE levels prior to the start of egg avoidance diet were lower in OITG children who passed DBPCFC at 4 months than in those who did not pass it. EW- and OVM-sIgE showed the best diagnostic performance in predicting DBPCFC result at 4 months. Levels above optimal EW-sIgE cut-off of 7.1 kU/L indicated 90% probability of failing DBPCFC.

CONCLUSION

This is the first demonstration of sustained unresponsiveness with a three-month egg-OIT protocol. Almost all treated subjects were desensitized and 37% achieved sustained unresponsiveness. EW-sIgE levels at the end of treatment predicted sustained unresponsiveness. This protocol shows a new approach to OIT for egg-allergic children.

Immunotherapy for food allergies: a myth or a reality?

Food allergy is a worldwide issue, with an estimated prevalence of 2-10%. An effective treatment is not available for people affected and the only management is the avoidance of the allergen. Oral immunotherapy and sublingual immunotherapy have been tested by several authors, in particular for milk, egg and peanuts allergy, with significant results in term of desensitization induction. The achievement of tolerance is by the contrary doubtful, with different results obtained. In this review, we reviewed protocols of oral and sublingual immunotherapy for food allergy published in literature, mainly against milk, egg and peanut. At present, immunotherapy does not represent the gold standard in the treatment of food allergy, even if it can desensitize patients.

A randomized, double-blind, placebo-controlled study of omalizumab combined with oral immunotherapy for the treatment of cow's milk allergy

BACKGROUND

Although studies of oral immunotherapy (OIT) for food allergy have shown promise, treatment is frequently complicated by adverse reactions and, even when successful, has limited long-term efficacy because benefits usually diminish when treatment is discontinued.

OBJECTIVE

We sought to examine whether the addition of omalizumab to milk OIT reduces treatment-related reactions, improves outcomes, or both.

METHODS

This was a double-blind, placebo-controlled trial with subjects randomized to omalizumab or placebo. Open-label milk OIT was initiated after 4 months of omalizumab/placebo with escalation to maintenance over 22 to 40 weeks, followed by daily maintenance dosing through month 28. At month 28, omalizumab was discontinued, and subjects passing an oral food challenge (OFC) continued OIT for 8 weeks, after which OIT was discontinued with rechallenge at month 32 to assess sustained unresponsiveness (SU).

RESULTS

Fifty-seven subjects (7-32 years) were randomized, with no significant baseline differences in age, milk-specific IgE levels, skin test results, or OFC results. At month 28, 24 (88.9%) omalizumab-treated subjects and 20 (71.4%) placebo-treated subjects passed the 10-g "desensitization" OFC (P = .18). At month 32, SU was demonstrated in 48.1% in the omalizumab group and 35.7% in the placebo group (P = .42). Adverse reactions were markedly reduced during OIT escalation in omalizumab-treated subjects for percentages of doses per subject provoking symptoms (2.1% vs 16.1%, P = .0005), dose-related reactions requiring treatment (0.0% vs 3.8%, P = .0008), and doses required to achieve maintenance (198 vs 225, P = .008).

CONCLUSIONS

In this first randomized, double-blind, placebo-controlled trial of omalizumab in combination with food OIT, we found significant improvements in measurements of safety but not in outcomes of efficacy (desensitization and SU).

Immunotherapy (oral and sublingual) for food allergy to fruits

BACKGROUND

Food allergy is an abnormal immunological response following exposure (usually ingestion) to a food. Elimination of the allergen is the principle treatment for food allergy, including allergy to fruit. Accidental ingestion of allergenic foods can result in severe anaphylactic reactions. Allergen-specific immunotherapy (SIT) is a specific treatment, when the avoidance of allergenic foods is problematic. Recently, studies have been conducted on different types of immunotherapy for the treatment of food allergy, including oral (OIT) and sublingual immunotherapy (SLIT).

OBJECTIVES

To determine the efficacy and safety of oral and sublingual immunotherapy in children and adults with food allergy to fruits, when compared with placebo or an elimination strategy.

SEARCH METHODS

The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, CINAHL, and AMED were searched for published results along with trial registries and the Journal of Negative Results in BioMedicine for grey literature. The date of the most recent search was July 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing OIT or SLIT with placebo or an elimination diet were included. Participants were children or adults diagnosed with food allergy who presented immediate fruit reactions.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by the Cochrane Collaboration. We assessed treatment effect through risk ratios (RRs) for dichotomous outcomes.

MAIN RESULTS

We identified two RCTs (N=89) eligible for inclusion. These RCTs addressed oral or sublingual immunotherapy, both in adults, with an allergy to apple or peach respectively. Both studies enrolled a small number of participants and used different methods to provide these differing types of immunotherapy. Both studies were judged to be at high risk of bias in at least one domain. Overall, the quality of evidence was judged to be very low due to the small number of studies and participants and possible bias. The studies were clinically heterogeneous and hence we did not pool the results. A study comparing SLIT with placebo for allergy to peach did not detect a significant difference between the number of patients desensitised at six months following a double-blind placebo-controlled food challenge (RR 1.16, 95% confidence interval (CI) 0.49 to 2.74). The second study, comparing OIT versus no treatment for apple allergy, found an effect on desensitisation in favour of the intervention using an oral provocation test at eight months, but results were imprecise (RR 17.50, 95% CI 1.13 to 270.19). Neither study reported data on evidence of immunologic tolerance. In both studies, the incidence of mild and moderate adverse events was higher in the intervention groups than in the controls. In the study comparing SLIT with placebo, patients in the intervention group experienced significantly more local adverse reactions than participants in the control group (RR 3.21, 95% CI 1.51 to 6.82), though there was not a significant difference in the number of participants experiencing systemic adverse reactions (RR 0.81, 95% CI 0.22 to 3.02). In the study of OIT, two of the 25 participants in the intervention group reported relevant side effects, whereas no participants in the control group reported relevant side effects.

AUTHORS' CONCLUSIONS

There is insufficient evidence for using OIT or SLIT to treat allergy to fruit, specifically related to peach and apple. Mild or moderate adverse reactions were reported more frequently in people receiving OIT or SLIT. However, these reactions could be treated successfully with medications.

The clinical utility of basophil activation testing in diagnosis and monitoring of allergic disease

The basophil activation test (BAT) has become a pervasive test for allergic response through the development of flow cytometry, discovery of activation markers such as CD63 and unique markers identifying basophil granulocytes. Basophil activation test measures basophil response to allergen cross-linking IgE on between 150 and 2000 basophil granulocytes in <0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In addition to clinical history, skin prick test, and specific IgE determination, BAT can be a part of the diagnostic evaluation of patients with food-, insect venom-, and drug allergy and chronic urticaria. It may be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti-IgE treatment or in the natural resolution of allergy. Basophil activation test may use fewer resources and be more reproducible than challenge testing. As it is less stressful for the patient and avoids severe allergic reactions, BAT ought to precede challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. In this EAACI task force position paper, we provide an overview of the practical and technical details as well as the clinical utility of BAT in diagnosis and management of allergic diseases.

Orally-Induced Intestinal CD4+ CD25+ FoxP3+ Treg Controlled Undesired Responses towards Oral Antigens and Effectively Dampened Food Allergic Reactions

The induction of peripheral tolerance may constitute a disease-modifying treatment for allergic patients. We studied how oral immunotherapy (OIT) with milk proteins controlled allergy in sensitized mice (cholera toxin plus milk proteins) upon exposure to the allergen. Symptoms were alleviated, skin test was negativized, serum specific IgE and IgG1 were abrogated, a substantial reduction in the secretion of IL-5 and IL-13 by antigen-stimulated spleen cells was observed, while IL-13 gene expression in jejunum was down-regulated, and IL-10 and TGF-β were increased. In addition, we observed an induction of CD4⁺CD25⁺FoxP3⁺ cells and IL-10- and TGF-β-producing regulatory T cells in the lamina propria. Finally, transfer experiments confirmed the central role of these cells in tolerance induction. We demonstrated that the oral administration of milk proteins pre- or post-sensitization controlled the Th2-immune response through the elicitation of mucosal IL-10- and TGF-β-producing Tregs that inhibited hypersensitivity symptoms and the allergic response.

Oral Food Challenges: The Design must Reflect the Clinical Question

Oral food challenges are the gold-standard diagnostic investigation for diagnosing food allergy. They allow a subject to consume an age-appropriate portion of allergenic food under surveillance to assess whether a reproducible immune-mediated adverse response is demonstrated. The specific design of food challenge must closely reflect the anticipated management step being considered. In clinical practice, food challenges are most commonly used to investigate the subject's status of allergy or tolerance to a food. However, other characteristics of food allergy are increasingly being investigated through recent studies. In particular, studies investigating food allergy prevention strategies, the impact of oral immunotherapy on subjects' threshold for allergic reactions and also their potential acquisition of long-term tolerance each utilize differing designs of oral food challenges to investigate their specific hypothesis. We examine how oral food challenges may be designed to assess specific characteristics of the food allergic response.

An Examination of Clinical and Immunologic Outcomes in Food Allergen Immunotherapy by Route of Administration

Allergen immunotherapy for the treatment of food allergy has been a subject of intensive study within the last 10 years. After an unsuccessful attempt with subcutaneous immunotherapy for peanut allergy, other routes with varying degrees of safety and efficacy have been tested for peanut, milk, and egg allergies. In this review, we summarize the results to date with oral immunotherapy, sublingual immunotherapy, and epicutaneous immunotherapy for the treatment of food allergy. While results of immunotherapy trials are promising, increases in efficacy are commonly associated with an increased side effect profile. There is a need for additional research beginning at the preclinical level to develop safe and effective treatments for food allergy.