Food Allergy

Purpose of Review

The goal of this review is to present an updated summary of the natural history of major childhood and adult food allergies and report recent advances in potential treatments for food allergy.

Recent Findings

The most common childhood food allergies are typically outgrown by adolescence or adulthood. However, peanut/tree nut allergies appear to more commonly persist into adulthood. Adults can develop new IgE-mediated food allergies; the most common is oral allergy syndrome. There are multiple different approaches being tried as possible treatments for food allergy.

Summary

The prevalence of food allergy appears to be increasing but the varied approaches to treatment are being actively pursued such that an approved modality may not be too far in the future.

     

Microbiome Diversity and Asthma and Allergy Risk

The prevalence of asthma and other allergic diseases is still increasing both in developed and developing countries. Allergic sensitization against common inhalant allergens is common and, although not sufficient, a necessary step in the development of allergic diseases. Despite a small number of proteins from certain plants and animals being common allergens in humans, we still do not fully understand who will develop sensitization and to which allergens. Environmental exposure to these allergens is essential for the development of sensitization, but what has emerged clearly in the literature in the recent years is that the adjuvants to which an individual is exposed at the same time as the allergen are probably an equally important determinant of the immune response to the allergen. These adjuvants act on all steps in the development of sensitization from modifying epithelial barriers, to facilitating antigen presentation, to driving T-cell responses, to altering mast cell and basophil hyperreactivity. The adjuvants come from biogenic sources, including microbes and the plants and animals that produce the allergens, and from man-made sources (anthropogenic), including unintended by-products of combustion and chemicals now ubiquitous in modern life. As we better understand how individuals are exposed to these adjuvants and how the exposure influences the likelihood of an allergic response, we may be able to design individual and community-level interventions that will reverse the increase in allergic disease prevalence, but we are not there yet.     

Biomarkers in Food Allergy

Purpose of Review

To familiarize the reader with the concept of precision medicine in food allergy by dealing with the current biomarkers for the diagnosis, prognosis, and management of the disease.

Recent Findings

Many efforts have been devoted in order to characterize reliable biomarkers able to identify specific phenotypes and endotypes in food allergy. Specific IgE (sIgE), sIgE/total IgE ratios, and T cell assays are just a few candidates that have been investigated over time. With the advent of omics sciences, a new era is commencing. A better understanding of pathogenesis of food allergy and mechanisms of action of the different therapeutic options will allow the accurate selection of the appropriate patient.

Summary

In the near future, advances in technologies and data interpretation will allow a better understanding of the pathogenesis of food allergy and the identification of proper biomarkers for a personalized treatment tailored on the specific patient’s profile.

     

Gastrointestinal Food Allergy in Infants

Food allergies are classified into three types, “IgE-mediated,” “combined IgE- and cell-mediated” and “cell-mediated/non-IgE-mediated,” depending on the involvement of IgE in their pathogenesis. Patients who develop predominantly cutaneous and/or respiratory symptoms belong to the IgE-mediated food allergy type. On the other hand, patients with gastrointestinal food allergy (GI allergy) usually develop gastrointestinal symptoms several hours after ingestion of offending foods; they belong to the cell-mediated/non-IgE-mediated or combined IgE- and cell-mediated food allergy types. GI allergies are also classified into a number of different clinical entities: food protein-induced enterocolitis syndrome (FPIES), food protein-induced proctocolitis (FPIP), food protein-induced enteropathy (Enteropathy) and eosinophilic gastrointestinal disorders (EGID). In the case of IgE-mediated food allergy, the diagnostic approaches and pathogenic mechanisms are well characterized. In contrast, the diagnostic approaches and pathogenic mechanisms of GI allergy remain mostly unclear.In this review, we summarized each type of GI allergy in regard to its historical background and updated clinical features, offending foods, etiology, diagnosis, examinations, treatment and pathogenesis. There are still many problems, especially in regard to the diagnostic approaches for GI allergy, that are closely associated with the definition of each disease. In addition, there are a number of unresolved issues regarding the pathogenic mechanisms of GI allergy that need further study and elucidation. Therefore, we discussed some of the diagnostic and research issues for GI allergy that need further investigation.     

Relationship Between Asthma and Irritable Bowel Syndrome: Role of Food Allergy

The increasing prevalence of both asthma and irritable bowel syndrome (IBS) are major health problems. One hundred twenty-five patients with asthma and 95 healthy subjects were included in this study. The rate of IBS was 29.6% and 12.7% (p < 0.005), and the incidence of food allergy was 7.2% and 2.1% (p > 0.05) respectively for asthma and control group. There was no significant association between asthma related parameters, IBS, and food allergy. There is not a single clear reason as to what causes IBS, so further studies are needed to clarify the potential pathogenic mechanisms underlying the association between IBS and asthma.     

Innovation in Food Challenge Tests for Food Allergy

Purpose of Review

This review incorporates findings from studies of oral food challenges (OFC) over the last decade and highlights the latest innovations and understanding of the procedure.

Recent Findings

PRACTALL guidelines are widely used in OFC research, but there is still no international consensus on the OFC protocol in clinical practice. Guidelines for performing OFC in clinical practice have been updated to include oral food challenges for infants. There have been advances in predictive models for outcomes and severity of reaction during OFC that take into account multiple clinical data as well as newer laboratory modalities. Low-dose OFC and eliciting threshold dose determination are being examined for additional diagnostic and therapeutic use in the management of food allergy. Quality-of-life considerations have also been reviewed, as well as post-OFC assessment and care.

Summary

The OFC remains an important diagnostic tool in the management of food allergy and in clinical research. Advances in the field should improve safety and broaden the clinical applications of this essential procedure.

     

Sesame Seed Food Allergy

The number of reports regarding sesame seed food allergy (SFA) has increased significantly worldwide over the past two decades, either due to a genuine increase in SFA or merely an increase in its awareness. Its prevalence is difficult to estimate due to the lack of well designed prospective population-based studies. Based on the available data, we estimate that SFA affects 0.1-0.2 % of the population, in areas where the food is available. Albeit this prevalence appears to be relatively low, it is approximately one-half of that of persistent cow's milk allergy. While only one fatality has been reported, the significant number of SFA patients presenting as anaphylaxis indicates the potential risk. Many reports based the diagnosis of SFA on sensitization criteria alone, particularly amongst atopic dermatitis patients. Elimination of sesame from the diet of these children utilizing such criteria is not justified, and may even increase the risk for developing SFA.     

Pathogenesis of Food Allergy in the Pediatric Patient

In the US and other developed countries, food allergy is a growing epidemic in pediatric populations with a substantial impact on health-related quality of life. As such, there are great efforts underway to unravel the mechanisms of oral mucosal tolerance and to better define the factors related to host and allergen exposure that contribute to the aberrant immune response leading to sensitization and clinical food allergy. Although more research is needed to eventually develop targeted treatment and prevention strategies, this review highlights our current understanding of the pathogenesis of IgE-mediated food allergy.     

The Genetics of Food Allergy

Purpose of Review

Food allergy likely arises from a complex interplay between environmental triggers and genetic susceptibility. Here, we review recent studies that have investigated the genetic pathways and mechanisms that may contribute to the pathogenesis of food allergy.

Recent Findings

A heritability component of food allergy has been observed in multiple studies. A number of monogenic diseases characterized by food allergy have elucidated pathways that may be important in pathogenesis. Several population-based genetic variants associated with food allergy have also been identified.

Summary

The genetic mechanisms that play a role in the development of food allergy are heterogeneous and complex. Advances in our understanding of the genetics of food allergy, and how this predisposition interacts with environmental exposures to lead to disease, will improve our understanding of the key pathways leading to food allergy and inform more effective prevention and treatment strategies.

     

Update on Food Allergy in Adults

Though much has been studied and written about food allergy, the majority of the available literature focuses on food allergies in the pediatric population. Unfortunately, it is likely that in regard to food allergies, adults are not just big children, and extrapolating findings from pediatric to adult patient populations might lead to erroneous assumptions. Thus, it is important to validate the correlation between pediatric and adult data, gather data regarding adult food allergy and understand the specific nuances of subsets of adults to better treat their food allergy. This review was conducted by identifying potentially relevant studies regarding food allergies in adults through electronic databases, including PubMed, Medline, and Google Scholar. The search terms included "allergy", "food" and "adults". Parameters of 19+ years of age were added to search terms and all journals were written in or translated to English. From these search results, focus was placed on studies from 2010 to 2012. This systematic update on food allergy in adults found that the evidence regarding prevalence, diagnosis and management of food allergies is very limited, with the majority of data derived from children and young adults.     

The Problem of Food Allergy in Childhood

Any physician whose responsibility it is to care for allergic children is aware that food can be an important allergen. Although ingestant sensitivity (food, drugs, drinks) is not so common as that of the inhalants, nevertheless, it can be and sometimes is the chief offender or a major or minor complicating factor in almost any allergic disorder in childhood.     

Japanese Guideline for Food Allergy

Food allergy is defined as “a phenomenon in which adverse reactions (symptoms in skin, mucosal, digestive, respiratory systems, and anaphylactic reactions) are caused in living body through immunological mechanisms after intake of causative food.”Various symptoms of food allergy occur in many organs. Food allergy falls into four general clinical types; 1) neonatal and infantile gastrointestinal allergy, 2) infantile atopic dermatitis associated with food allergy, 3) immediate symptoms (urticaria, anaphylaxis, etc.), and 4) food-dependent exercise-induced anaphylaxis and oral allergy syndrome (i.e., specific forms of immediate-type food allergy).Therapy for food allergy includes treatments of and prophylactic measures against hypersensitivity like anaphylaxis. A fundamental prophylactic measure is the elimination diet. However, elimination diets should be conducted only if they are inevitable because they places a burden on patients. For this purpose, it is highly important that causative foods are accurately identified. Many means to determine the causative foods are available, including history taking, skin prick test, antigen specific IgE antibodies in blood, basophil histamine release test, elimination diet test, oral food challenge test, etc. Of these, the oral food challenge test is the most reliable. However, it should be conducted under the supervision of experienced physicians because it may cause adverse reactions such as anaphylaxis.