Patch testing with egg represents a useful integration to diagnosis of egg allergy in children with atopic dermatitis

Is Food-Triggered Atopic Dermatitis a Form of Systemic Contact Dermatitis?

Food allergy in atopic dermatitis is mediated by complex immune interactions between genetics, diet, environment, and the microbiome. When contact between inflamed skin and food antigens occurs, contact hypersensitivity can develop. Consequently, systemic contact dermatitis (SCD) can occur after ingestion of allergenic foods or food additives in the setting of a Th2 response with CLA-positive T cells, triggering dermatitis where skin resident memory lymphocytes reside. This phenomenon explains food-triggered dermatitis. Atopy patch tests (APTs) detect sensitization to food proteins responsible for SCD, which in turn can be confirmed by oral food challenge with delayed interpretation. We summarize the literature on using APTs to identify foods for oral challenge with dermatitis as an outcome. In dermatitis patients at risk for Th2 skewing based on a history of childhood-onset flexural dermatitis, shared decision-making should include a discussion of identifying and avoiding food and food additive triggers, as well as identifying and avoiding all contact allergens, prior to initiation of systemic therapy for dermatitis.

The diagnostic value of APT for food allergy in children: a systematic review and meta-analysis

BACKGROUND

The role of atopy patch test (APT) in the diagnosis of food allergy (FA) remains largely controversial. In our meta-analysis, we aimed to evaluate the accuracy of APT for diagnosing FA in children.

METHODS

Pubmed, Embase and Cochrane Library were searched for studies regarding the diagnostic value of APT for FA in children compared to oral food challenge (double-blind placebo-controlled food challenge and/or open food challenge). The last search was conducted on November 11, 2017. Two reviewers independently screened relevant studies and assessed the quality by QUADAS-2. Meta-analysis was performed to calculate the pooled sensitivity, specificity, DOR (diagnostic odds ratio), PLR (positive likelihood ratio), NLR (negative likelihood ratio) with their 95% confidence intervals (CIs). Subgroup analyses were conducted according to different food allergens, atopic dermatitis, gastrointestinal symptoms, and age younger than 3 years.

RESULTS

Forty-one studies were included in the meta-analysis. The pooled sensitivity, specificity, PLR, NLR and DOR were 50.30% (95% CI 48.40%-52.30%), 86.60% (95% CI 85.30%-87.80%), 3.405 (95% CI 2.594-4.470), 0.545 (95% CI 0.469-0.634) and 7.528 (95% CI 5.507-11.206), respectively. However, for children with FA-related gastrointestinal symptoms, the pooled sensitivity and specificity were 57.40% (95% CI 52.10%-62.50%) and 91.50% (95% CI 88.30%-94.10%) respectively.

CONCLUSIONS

Our findings suggest that APT is specific but not sensitive for diagnosing FA in children, especially in children with FA-related gastrointestinal symptoms.

Eosinophilic Esophagitis From an Allergy Perspective: How to Optimally Pursue Allergy Testing & Dietary Modification in the Adult Population

Eosinophilic esophagitis (EoE) is a clinicopathologic condition characterized by symptoms of esophageal dysfunction and eosinophil-predominant inflammation. In adults, the three most common treatment options are swallowed steroids, elimination diets, and periodic esophageal dilations. Many different elimination diets have been studied in adults, including elemental diets, allergy testing-directed diets, and empiric elimination diets. This article will review the existing data on these dietary therapies and will propose an approach to dietary management in adult EoE.

Food allergy testing in eosinophilic esophagitis: what the gastroenterologist needs to know

Eosinophilic esophagitis (EoE) is a clinicopathologic disease of increasing prevalence in children and adults. The triggering antigen in EoE is often a food that initiates a cascade of Th2-associated interleukins such as interleukin-5 and interleukin-13 and chemokines such as eotaxin-3 as well as esophageal eosinophilia and mastocytosis. Amino acid-based formulas have high efficacy rates in EoE and constitute the first evidence for food-triggered esophageal eosinophilia. Animal models have demonstrated the sufficiency of food antigens in triggering both the inflammatory and remodeling complications of EoE. Food elimination diets that are followed by single food introduction with repeat biopsy have proven the efficacy of empiric and allergy testing based elimination diets in children and adults. Although the ideal allergy test for identifying food antigens in EoE remains to be elucidated, the utility of food skin prick combined with atopy patch testing has been shown in large pediatric cohorts. By comparison, smaller, non-U.S. adult cohorts have not had similar results. Currently, a positive test on food allergy evaluation suggests a food trigger for EoE but does not substitute for biopsy-based tissue evaluation after food removal and reintroduction. The higher rates of food anaphylaxis in children with EoE, potential loss of tolerance to immunoglobulin E-positive foods that can occur with food avoidance, and the high rates of other atopic diatheses in EoE subjects all support the evaluation of EoE subject by an allergist, consideration for allergy testing, and an integrated approach by allergists, gastroenterologists, and pathologists in EoE management.

Food allergy and anaphylaxis

Food allergy is a common cause of anaphylaxis, and its incidence is rising. The development of allergy is multifactorial, and the mechanisms of tolerance are complex. The natural history of food allergy varies by causative food; some allergies are mostly outgrown, while others are usually life-long. Anaphylaxis caused by food allergy may differ clinically from other causes of anaphylaxis. Death is usually caused by respiratory failure, and patients who have asthma are at greatest risk for severe reactions. At this time, avoiding allergenic triggers, and when that fails, timely administration of epinephrine, are the main approaches to food allergy. Although several experimental medications promise to dramatically change the field of food allergy, none of these treatments are currently available outside of research settings.

The diagnosis and management of egg allergy

Egg allergy is a common food hypersensitivity in children. Atopic dermatitis represents the main clinical manifestation in infancy. On first exposure, many of these infants present with urticaria, angioedema, or anaphylaxis. The role of egg allergy in gastrointestinal conditions is less well understood. The "gold standard" for the diagnosis of egg allergy is the double-blind, placebo-controlled food challenge. Diagnostic cut-off levels have been defined for food-specific serum immunoglobulin E antibody level and skin prick test wheal diameter that predict an adverse challenge outcome. This has significantly reduced the need for formal food challenges. Atopy patch testing, in conjunction with immunoglobulin E-based tests, may further improve the accuracy of predicting a positive challenge. The treatment of egg allergy consists of dietary elimination, or a maternal elimination diet in breast-fed infants. Approximately two thirds of infants with egg allergy will become tolerant by 7 years of age.