Allergies |4. Food allergy in childhood

F flood allergy is a common allergic manifestation in early childhood.1There has been a significant increase in public awareness of food allergies, as highlighted in the reports of the media in Australia and abroad. However, some doctors are skeptical about the role of food allergies in various clinical, such as atopic dermatitis, colic and gastroesophageal reflux in infancy, despite a growing body of evidence that food allergy may syndromes contribute to these conditions.2 our article aims to help general practitioners and other physicians to understand the principles of diagnosis and treatment of food allergy in childhood, and suggests when to refer patients to specialist opinion.

How common is food allergy?

Glossary

amino acid-based formula (AAF). Elemental infant formula in which the ingredients are present in its digested (for example, amino acids and glucose). These formulas are considered the most available hypoallergenic and are useful for children with severe forms of food allergy, including cow’s milk allergy, multiple food allergies and food protein-induced enterocolitis.

extensively hydrolysed formula (EHF ). Cow’s milk based on a formula that has been treated with enzymes to break down most of the proteins that cause allergy symptoms in children with cow’s milk. It is important to note that partially hydrolyzed formula is not indicated for the treatment of children allergic to cow’s milk.

eosinophilic esophagitis. eosinophilic infiltration of the esophagus, which is generally devoid of eosinophils. It can occur as part of a greater involvement of the gastrointestinal tract.

epitope. an antigenic determinant (the structural component of an antigen molecule that is responsible for specific interaction with the antibody).

oral allergy syndrome symptoms of food allergy-related mouth and throat -. Usually in the form of oral itching, swelling of the lips, lip angioedema and edema of the glottis occasionally – as a result of direct contact with the offending food. Some doctors restrict the use of the term syndrome pollen-food allergy.

Toll-like receptors. pattern recognition receptor on cells of the innate immune system that recognize conserved bacterial structures. dependent Toll receptor signal provided by intestinal bacteria can inhibit the development of allergic to food antigens by stimulating regulatory T cells responses.

The prevalence of food allergies seems to be increasing in industrialized countries, although reliable data, based on the population are limited. Both figures of prevalence and spectrum of food allergens vary considerably across geographic regions, and is believed to reflect the change in diet between the different cultures.1However has been estimated that up to 6% of children under 3 years of age are affected by food infants with atopic allergies.3 first-degree relative they are at increased risk of allergy.

Recent studies have sought to confirm the anecdotal evidence of an increased incidence of peanut allergy. In a UK study, Grundy et al found an increase in reported peanut allergy 0.5% to 1.5% in two sequential cohorts of early childhood in the same geographical area, surveyed six years apart.4

Although atopic disorders have a significant genetic basis, it is believed that the recent increase is due to a change in environmental factors, including changes in diet and reducing exposure to infection early childhood.

What is food allergy?

Food allergy is defined as an abnormal immune reaction to food proteins that cause an adverse clinical reaction. food allergy needs to be distinguished from other types of adverse reactions to food, including:

  • food intolerance (eg lactose malabsorption);

  • pharmacological reactions food components (eg vasoactive amines);

  • food poisoning (eg food-borne bacterial gastroenteritis); and

  • toxic reactions (for example, staphylococcal enterotoxin).

It is estimated that around a quarter of the population will have an adverse reaction to food (including food allergy is only one type) during his lifetime, especially during childhood early and childhood.5

the best characterized form of food allergy is mediated by specific IgE antibodies to food. However, there is growing recognition of IgE mediated food allergy, often through reactions to cow’s milk, soy or wheat. This is believed to result from the immune mechanisms mediated by cells that are still poorly understood. This limits the ability to use skin prick tests (SPT) and serological tests for the diagnosis of allergic reactions to foods mediated by IgE. At present, the most reliable to assess food allergies IgE mediated method is not a formal sequence removal target diet and rechallenge after a period of symptomatic improvement.

Common food allergens

Although, in theory, any food protein can have the ability to sensitize the immune system, over 90% of food allergies mediated by IgE children is caused by just eight foods: cow’s milk, soy, egg chicken, peanuts, tree nuts (and seeds), wheat, fish and shellfish. Typically, food allergens are glycoproteins that are relatively resistant to digestion and kitchen. A large number of food allergens have been identified and characterized (eg β lactoglobulin in cow’s milk, ovomucoid [Gal d 1] egg and Arachis hypogaea allergen 1 [Ara h 1] in peanuts). In each of these proteins, specific epitopes (structural components of the antigen molecule) have been mapped interacting with specific IgE antibody to food or T cell receptors Further characterization of these epitopes will be essential for the development of hypoallergenic vaccines food or genetically modified foods. Epitope also appear to have a prognosis of food allergies paper. Linear epitopes are typically associated with long-term, persistent allergies, while conformational (three-dimensional) epitopes may be associated with more transient allergies.6

When Suspect food allergy?

angioedema lip in a child with nut allergy

Allergic reactions to foods encompass a spectrum of symptoms, ranging from minor skin lesions to life-threatening anaphylactic reactions (Table 1, Table 2) 0.1 the relationship between exposure to food and clinical reaction may be obvious, as in an acute IgE-mediated reaction to peanut ingestion. In such instances, removal of the food will prevent further symptoms. However, the total contribution of a food antigen multifactorial conditions such as atopic dermatitis, eosinophilic esophagitis, gastroesophageal reflux disease, or infantile colic is less known. In these cases, a food protein may induce the disorder or trigger a flare, but the offending antigen removal while reducing the severity of a disease, may not result in complete remission.

The diagnosis of food allergies requires a detailed dietary history, including the time interval between food intake and the onset of symptoms, to establish the link between exposure and allergic response. Acute reactions usually occur within 2 hours of ingestion of a food, and typical presentations include urticaria, angioedema, anaphylaxis or vomiting. Delayed onset reactions develop within 24-72 hours after ingestion of food and are more difficult to define. The clinical presentations of late reactions include atopic dermatitis, infantile colic, reflux esophagitis, diarrhea and constipation.

atopic dermatitis

Atopic dermatitis in childhood is closely associated with both IgE mediated food allergy and non-IgE mediated. The association is stronger in newborns with moderate to severe eczema that begins before 12 months of age (Table 3). As food allergy often resolves in early childhood, the relationship between food allergy and eczema is much weaker in older children and adults than in children.

Cows milk allergy

allergy to cow’s milk (CMA) affects about 2% of children under 2 years of age in countries industrialized and is the most common form of food allergy in this age group. CMA can present with IgE or non-IgE mediated manifestations, up 50% thought not IgE mediated. Symptoms and syndromes that should alert the clinician to the possibility of CMA are summarized in Table 1. It is important to note that CMA is not confined to formula-fed infants, such as milk proteins intact cows (as β- lactoglobulin and α lactalbumin) found in breast milk. In most children with CMA, allergic response develops within 4 weeks of starting the cows milk formula, 8 and in the vast majority of cases resolve by CMA 3 years edad.9

rich food protein-induced gastrointestinal syndromes

gastrointestinal syndromes induced by food proteins are increasingly recognized in young children. This group of disorders is presented with related to various parts of the gastrointestinal tract, including symptoms:

  • small intestine: babies with food-induced enteropathy proteins present with diarrhea and developmental delay ;

  • colon: the most common low-grade rectal bleeding in young children Proctocolitis cause is food-induced proteins; 10 and 11

  • small intestine and colon: enterocolitis induced by food proteins (FPIES) syndrome is characterized by more extensive disease of the small intestine and colon (see below) 0.12

Other gastrointestinal, such as eosinophilic esophagitis disorders have also been shown to be associated with food allergies. This condition is discussed in a separate article Focus this problem.13

FPIES often presents with severe diarrhea, vomiting, dehydration and lack of growth. In about 20% of patients, the presentation can be dramatic, with acute episodes of dehydration that causes circulatory collapse and shock.12 allergic to multiple food proteins is common in FPIES, and even cow’s milk and soy are considered the main causative allergens, children can present with FPIES after the first exposure to grains (such as oats or wheat), rice or poultry.12Interestingly, FPIES not seem to occur in breastfed babies, suggesting that larger amounts of causal to cause inflammation of the intestinal mucosa antigen required. By contrast, food protein induced enteropathy and Proctocolitis can occur in either formula or breast fed infants.10 11

multiple food allergy

multiple food allergies (formerly known as “multiple protein intolerance food of childhood”) is characterized by allergic reactions to food late into breast milk emergence reactions, formula (including formula completely hydrolyzed [EHF] and soybean) and a wide range of solid foods. Infants with multiple food allergy may present with symptoms such as intermittent vomiting, diarrhea, poor appetite, irritability, severe atopic dermatitis or lack of thrive.14 resolution of symptoms occurs only after the introduction of a formula based amino acids (AAF). Such babies have complex nutritional requirements and principles should be referred for specialist assessment and management.

tests that aid in the diagnosis? skin prick tests

skin prick wheal test in an 8 month old baby

the baby had a history of immediate reaction to cow’s milk and egg hypersensitivity. Skin tests also showed positive responses to a variety of other foods, such as cashew, peanuts, sesame seeds and wheat reactions.

SPT provides a means of easily accessible and inexpensive evaluation of IgE mediated food allergy. There is no minimum age for SPT, which can be performed in infants and young children with useful results. A result of positive skin test has a relatively low positive predictive value (ie, a significant number of patients with a positive result may be asymptomatic) but a skin prick test has a high negative predictive value (ie, a result negative indicates that the IgE mediated food allergy is unlikely). The non-IgE mediated mechanisms can not be assessed by SPT and may require formal food tests to identify the food responsible antigen firmly. points making diagnosis of SPT defined for several food allergens (Table 4).

Specific food IgE levels in serum

levels of serum antibodies specific for food IgE can be used as an alternative to seamless tubes in the evaluation food IgE-mediated allergy, although laboratory reference ranges vary widely.20 , 21Low serum levels of IgE specific food can be found in healthy individuals without clinical reactivity to food (ie, it is not awareness, but not allergy). serum specific food IgE should be quantified in kU A / L (units are kU / L for total IgE and Ku A / L for specific IgE antibodies allergen ) rather than expressed in semiquantitative scale (as low / medium / high), as diagnostic sampling points are available for several major food allergens (Table 4).

test atopy patch

eosinophilic esophagitis

lining of the esophagus (hematoxylin -eosina, original magnification × 400). Courtesy Associate Professor C W Chow, Royal Children’s Hospital, Melbourne, VIC.

In recent years, the atopy patch test (APT) has been introduced as a diagnostic tool for late-onset food allergies, including atopic dermatitis and eosinophilic esophagitis. The APT is based on skin responses, mediated by after epicutaneous application of food allergens cells. It has been suggested that the APT, in conjunction with tests based on IgE, significantly improves the diagnostic accuracy of allergy testing, again reducing the need for challenges.17 formal However, the role of the patch test in the diagnosis food allergy requires further clarification and is an area of ​​ongoing research.

IgG antibodies to food antigens

IgG antibodies to food are commonly detectable in adult patients and healthy, independent children presence or absence of symptoms related feeding. There is currently no evidence that the levels of IgG antibodies specific serum foods are clinically useful for diagnosing food allergy in children, since it is believed that simply indicate previous exposure to the food in question, but this is still an area of investigation.

challenge and food diagnostic elimination

In patients with SPT equivocal or results of specific IgE to foods below points making diagnostic confirmation diagnosis only be achieved by challenge.22 food challenge formal protocols are based on increasing oral doses of food allergens, from a low dose. The doses are administered at predetermined time intervals until the first symptoms appear. The challenges are usually performed in the hospital because of the risk of anaphylaxis. However, the challenges of houses made by parents may be appropriate in patients with mild allergic reactions and a negative skin test, since the risk of a severe immediate reaction or anaphylaxis is minimal. open challenges are usually sufficient in clinical practice, as long as the symptoms can be assessed objectively. Double-blind, placebo-controlled food challenges are used for patients with subjective symptoms or as part of the investigation.

Elimination diets are also an important research diagnosis of late-onset food allergies step, which are usually not mediated by IgE (Table 5). Decisions on whether to conduct formal food testing and whether to perform them in the hospital are influenced by the possibility of food allergy – based on the history and interpretation of the results of allergy tests -. And the perceived risk of a severe reaction in the challenge

gastrointestinal biopsies

Endoscopic biopsies of the upper gastrointestinal tract and lower can provide important diagnostic information in patients with suspected syndromes food allergy, such as eosinophilic esophagitis, food protein induced enteropathy or child proctocolitis. Ideally, biopsies should be obtained before starting treatment or elimination diets corticosteroids. Endoscopy is also useful to rule out conditions such as celiac disease, which can be considered in the differential diagnosis. In patients with severe childhood constipation, rectal biopsy is useful for detecting Hirschsprung’s disease or eosinophilic Proctocolitis.

Management

The fundamental principle of the management of food allergy is to avoid the offending antigen. Misdiagnosis is likely to result in unnecessary dietary restrictions, which, if prolonged, may adversely affect the nutritional status and growth of the child. For patients who require prolonged restrictive diets, a formal dietary assessment is recommended to ensure that nutritional requirements are met.

Cows milk allergy

there is no complete agreement on the first-line treatment for children with CMA. Approximately 10% of children with CMA not tolerate EHF, presumably because of the residual allergenicity of the peptide molecules and larger proteins present in the formula, and AAF may be necessary. The current recommendation Pharmaceutical Benefits Scheme Australia (PBS) which is a soy-based formula should always be tested before prescribing the EHF. However, a statement of recent European position has recommended that the formula based on soy should not be used as first-line treatment for infants under 6 months of age, because of a high level of allergy concurrent soybean and questions about the suitability of soy formula in this age group.27 in Europe, the EHF is the formula of first-line treatment of CMA – except in infants with suspected allergy to multiple foods, which require RAA . (Most children will not tolerate several foods formula at 18 months and may cease AAF 3 years of age.28) In the light of the recommendations, it is possible that the current recommendation PBS Australia for review .

self-administered injectable epinephrine

fact or fiction? – True or false

1. Children often develop tolerance to cow’s milk, egg, soy and wheat by school age, while allergy to peanuts, tree nuts and shellfish are more likely that is permanent (V / F)

2. food allergy does not occur in exclusively breastfed infants (T / F)

3. the symptoms of allergy food can manifest as colic, gastroesophageal reflux or atopic dermatitis in infancy (V / F)


Over 90% of fatal anaphylactic reactions or nearly fatal to food are caused by peanuts and tree nuts.29 intramuscular injection of epinephrine is the treatment of choice for anaphylaxis, regardless of etiology. EpiPen auto-injectors (CSL Limited, Melbourne, VIC) containing a single dose of adrenaline are available for the treatment of anaphylaxis. The doses usually recommended by the specialized agencies (such as the Australasian Society of Clinical Immunology and Allergy [ASCIA]) differ from those of the manufacturer’s product information. In Australia, it is recommended that junior EpiPen (0.15 mg) prescribed for patients weighing 10-20 kg and EpiPen (0.30 mg) for patients over 20 kg.

The use of adrenaline auto-injectors in Australian children has increased by 300% in the last 5 years, with 1 in 544 Australian children under 10 years using them.30 This may indicate that EpiPen patients prescribed in low-risk categories, but there is no population data are currently available on the appropriateness of its use EpiPen in Australia.

guidelines published by ASCIA recommend that patients with previous food-induced anaphylaxis should be provided with a EpiPen.31 Your recipe should also be considered for patients with a history of significant generalized allergic reaction and at least one of the following risk factors:. the age of 5 years history of asthma, allergy to peanuts or nuts, or limited to emergency medical care

access

Parents and caregivers to carry an adrenaline auto-injector should have anaphylaxis action plan and be trained in using the device. In addition, patients should be reviewed periodically to assess the continuing need for an EpiPen and strengthen its proper use.

Can prevent food allergies?

One hypothesis to explain the increased incidence of sensitization to food allergens is that the reduction of infections in early childhood or exposure to microbial products (eg endotoxins) can prevent the development of early immunoregulatory responses. This leaves the immune system more susceptible to inappropriate reactivity against innocuous antigens, resulting in “allergic”

reaction.32

postnatal development of mucosal immune homeostasis is influenced by the type present in commensal microbiota neonatal period (for example, the predominance of bifidobacteria in infants fed breast milk may have a protective effect against food allergy) and the initial time and dose of diet antigens.33 recent research suggests that signals toll-dependent receptor provided by intestinal bacteria can inhibit the development of allergic responses to food antigens by stimulating regulatory T cells.34

a recent study found that differences in the gut microbiota neonatal development of atopy precede, suggesting a role for intestinal commensal bacteria in preventing allergy.35 This research has led to the hypothesis that probiotics can promote oral tolerance. Perinatal administration of Lactobacillus casei GG has been reported to reduce the incidence of atopic dermatitis, but not food allergy in children at risk during the first 4 years of life.

Exclusive breastfeeding seems to have a preventive effect on the early development of asthma and atopic dermatitis up to 2 years old, but the evidence for prevention of food allergies is less clear. The late introduction of solid foods until after 4 months is believed to partially protects babies develop food allergies, but this has recently been questioned.36 If exclusive breastfeeding is not possible, a hydrolyzed formula is recommended during the first 4 months of life of infants at high risk of food allergy (ie, those with a first degree relative atopic) .37Currently no evidence for the protective role of maternal elimination diets during pregnancy.25

future therapeutic options

Several new treatments for food allergy are being tested. However, none of these are currently available outside of clinical trials. The role of immunotherapy38 injection for the treatment of food allergy is limited due to the high risk of inducing anaphylaxis. By contrast, sublingual immunotherapy with food allergens can be better tolerated in children, but their clinical efficacy has not yet been clearly demonstrated.

anti-IgE

recombinant (omalizumab) has been used to treat limited food allergy success. A recent study of patients with severe peanut allergies showed an increased tolerance threshold (on average between half nine peanuts) in oral food challenge, after receiving a course of omalizumab.39 Although a protocol this guy could protect a person with severe peanut allergy against most accidental ingestions of peanuts, therapy is expensive, requires regular administration, and is not currently approved in Australia for the treatment of food allergy.

Finally, there is the possibility of producing genetically modified foods from which the major allergens have been removed.40

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