Chemical immunology and allergy最新文献

Food allergy is a known trigger of anaphylaxis. Although the awareness of food allergies has improved, food-related allergic reactions and anaphylaxis still commonly occur. The recognition of anaphylaxis, its prompt treatment, and patient education are important for the prevention of future food reactions. Patients and health care providers should also recognize the importance of epinephrine as the primary treatment of anaphylaxis. When food-related anaphylaxis occurs, patients should receive education regarding their food allergies, an epinephrine auto-injector, and follow-up with a food allergy specialist to reduce the risk of future food-related reactions.

Among grains and legumes, wheat and soybean are the most frequent and well-characterized allergenic foods. Wheat proteins are divided into water/salt-soluble and water/salt-insoluble (gluten) fractions. The most dominant allergen in the former is α-amylase/trypsin inhibitor, which acts as an inhaled allergen causing baker's asthma. Gluten allergens, including ω-5 gliadin and high- and low-molecular-weight glutenins, contribute to wheat-dependent exercise-induced anaphylaxis in adults and immediate-type wheat allergies, including anaphylaxis, in children. Recently, wheat allergies exclusively caused by hydrolyzed wheat proteins or deamidated glutens have been reported, and the presence of unique IgE-binding epitopes has been suggested. Soybean allergens contributing to immediate-type allergic reactions in children are present in seed storage proteins, namely Gly m 5, Gly m 6 and Gly m 8. However, pollen-related soybean allergy in adults is caused by the Bet v 1 homolog of soybeans, Gly m 4. Taken together, the varying clinical manifestations of wheat and soybean allergies are predominantly caused by their different allergen components.

Fruit and vegetable allergies are the most prevalent food allergies in adolescents and adults. The identification of the allergens involved and the elucidation of their intrinsic properties and cross-reactivity patterns has helped in the understanding of the mechanisms of sensitisation and how the allergen profiles determine the different phenotypes. The most frequent yet contrasting fruit and vegetable allergies are pollen-food syndrome (PFS) and lipid transfer protein (LTP) syndrome. In PFS, fruit and vegetable allergies result from a primary sensitisation to labile pollen allergens, such as Bet v 1 or profilin, and the resulting phenotype is mainly mild, consisting of local oropharyngeal reactions. In contrast, LTP syndrome results from a primary sensitisation to LTPs, which are stable plant food allergens, inducing frequent systemic reactions and even anaphylaxis. Although much less prevalent, severe fruit allergies may be associated with latex (latex-fruit syndrome). Molecular diagnosis is essential in guiding the management and risk assessment of these patients. Current management strategies comprise avoidance and rescue medication, including adrenaline, for severe LTP allergies. Specific immunotherapy with pollen is not indicated to treat pollen-food syndrome, but sublingual immunotherapy with LTPs seems to be a promising therapy for LTP syndrome.

Approximately one-third of children with severe atopic eczema suffer from a food allergy, whereas in adult patients, food allergies are rare. In child patients, three different clinical reaction patterns can be differentiated as follows: (1) immediate-type reactions, (2) isolated late eczematous reactions, and (3) combined immediate-type and late eczematous reactions. In childhood food allergies, food allergens, such as cow's milk or hen's egg, are primarily responsible for allergic reactions, while in adolescents and adults, food allergies often develop consecutively after primary sensitization to pollen allergens. Dysfunctions in the epidermal barrier seem to be vitally important in the development of food allergies in patients with atopic eczema by facilitating sensitization after epicutaneous allergen exposure. Further investigation is required to determine the role of intestinal epithelial barrier defects in the pathogenesis of these allergies as well as the genetic characteristics associated with an increased risk of food allergy. The diagnosis of eczematous reactions to food requires a careful diagnostic procedure, taking into account a patient's history and sensitization patterns. The clinical relevance of sensitization often has to be proven by an oral food challenge, with the rating of the skin condition by validated scores after 24 h and the later evaluation of the eczematous reaction.

Accurately diagnosing patients with suspected food allergy is obviously critically important. The patient's health may be compromised if problem foods are left in the diet, while nutrition and quality of life may be negatively affected if foods are unnecessarily removed from the diet. In some patients, the diagnosis is very straightforward, such as with anaphylaxis with the first known exposure to peanut, but in many cases, the diagnosis will not be clear based on the history, skin tests, and serologic tests, especially because these tests often yield falsely positive results. In these instances, further testing will be needed, typically including diagnostic elimination diets and/or oral food challenges, which are the gold standard for the diagnosis of food allergy.

The labeling of allergenic foods is an important public health measure to assist food-allergic consumers in avoiding foods that can cause allergic reactions. The regulatory framework for such labeling depends upon the selection of priority allergenic foods, which vary among countries. Most countries include milk, eggs, fish, crustacean shellfish, peanuts, tree nuts, soybeans, and cereal sources of gluten on the priority allergenic foods list, as recommended by the Codex Alimentarius Commission. However, a variety of other foods appear on the priority lists of some countries but not on others. Sesame seeds, molluscan shellfish, buckwheat, and mustard are identified in two or more countries. In most countries, all ingredients derived from these priority allergen sources must also be declared on labels by source. However, exemptions exist for some ingredients in some countries but not in others. Detection methods are critical for the enforcement of allergen labeling regulations and for the investigation of allergic reactions in the community by public health officials. The development of detection methods has advanced considerably over the past several decades and will be briefly reviewed in this chapter. Because of the emphasis on labeling and the development of detection methods, the ingredient statement on packaged food labels now contains more information than ever before to assist food-allergic consumers.

There is currently no well-established disease-modifying treatment for food allergy, so management relies upon strict avoidance of food allergen(s), implementation of risk minimisation strategies to avoid inadvertent exposure and allergic reactions, and prompt management of acute allergic reactions, should they occur. The pharmacological management of acute food-induced allergic reactions is dependent on the underlying pathophysiology of the allergic reaction and the severity of clinical symptoms and signs. Mild to moderate symptoms of an immunoglobulin E-mediated acute allergic reaction may be treated effectively with an oral anti-histamine. In patients exhibiting the clinical features of anaphylaxis, adrenaline is the only first-line therapy recommended by expert consensus. Adjunctive therapies, including anti-histamines, beta-agonists and glucocorticoids, may be used in the subsequent management of immunoglobulin E-mediated anaphylaxis. Here, we present the current recommendations for the pharmacological management of acute food-induced allergic reactions, together with a summary of the evidence supporting these recommendations.

Allergy to peanut and tree nuts is a major worldwide health concern. The prevalence of these allergies may be increasing, but the reasons for these increases remain unclear. This group of foods accounts for a large proportion of severe and fatal food-allergic reactions. These allergies present most often during childhood but can occur at any age. Resolution is possible but uncommon, and frequent lifetime reactions caused by accidental ingestion are a serious problem. The major allergens of peanut and most tree nuts have been identified, allowing for insights into patient diagnoses, clinical outcomes, and potential future immunotherapies.

Gastrointestinal food allergies present during early childhood with a diverse range of symptoms. Cow's milk, soy and wheat are the three most common gastrointestinal food allergens. Several clinical syndromes have been described, including food protein-induced enteropathy, proctocolitis and enterocolitis. In contrast with immediate, IgE-mediated food allergies, the onset of gastrointestinal symptoms is delayed for at least 1-2 hours after ingestion in non-IgE-mediated allergic disorders. The pathophysiology of these non-IgE-mediated allergic disorders is poorly understood, and useful in vitro markers are lacking. The results of the skin prick test or measurement of the food-specific serum IgE level is generally negative, although low-positive results may occur. Diagnosis therefore relies on the recognition of a particular clinical phenotype as well as the demonstration of clear clinical improvement after food allergen elimination and the re-emergence of symptoms upon challenge. There is a significant clinical overlap between non-IgE-mediated food allergy and several common paediatric gastroenterological conditions, which may lead to diagnostic confusion. The treatment of gastrointestinal food allergies requires the strict elimination of offending food allergens until tolerance has developed. In breast-fed infants, a maternal elimination diet is often sufficient to control symptoms. In formula-fed infants, treatment usually involves the use an extensively hydrolysed or amino acid-based formula. Apart from the use of hypoallergenic formulae, the solid diets of these children also need to be kept free of specific food allergens, as clinically indicated. The nutritional progress of infants and young children should be carefully monitored, and they should undergo ongoing, regular food protein elimination reassessments by cautious food challenges to monitor for possible tolerance development.

Although awareness that food can cause adverse symptoms and even death in some individuals has been present since the times of Hippocrates, it was not until the seminal experiment of Prausnitz that the investigation of food allergy had a more scientific basis. In the first half of the 20th century, there were periodic reports in the medical literature describing various food allergic reactions. Until the studies of Charles May and colleagues in the mid- to late '70s, there was a great deal of skepticism in the medical world about the relevance of food allergy and how to diagnose it, since standard skin testing was known to correlate poorly with clinical symptoms. With the introduction of the double-blind, placebo-controlled oral food challenge by May, the study of food allergy has become evidence based, and tremendous strides have been made in the study of basic immunopathogenic mechanisms and natural history as well as in the diagnosis and management of food allergies. Today, various IgE- and non-IgE-mediated food allergic disorders have been well characterized, and efforts to reverse these allergies using various immunotherapeutic strategies are well under way.