Influence of age on the outcome of the atopy patch test with food 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.

Patch testing for noncontact dermatitis: the atopy patch test for food and inhalants

The atopy patch test (APT) is defined as a patch test procedure to assess delayed type hypersensitivity reactions against those protein allergens known to elicit IgE-mediated type I reactions in atopic patients. This patch test procedure uses intact protein allergens instead of haptens in an optimized test setting and with a special reading key. It may be clinically useful especially for atopic dermatitis, as the currently available test procedures either target the wrong reaction type (type I and not type IV) or use the wrong allergens (haptens and not protein allergen). A positive APT reaction correlates with a positive lymphocyte transformation test and allergen-specific Th2 cells in the peripheral blood. As even small changes in the test procedure influence the sensitivity, specificity, and reproducibility of the APT, the European Task Force on Atopic Dermatitis (ETFAD) has developed a standardized APT technique: Intact protein allergens, purified in petrolatum, are applied in 12-mm-diameter Finn chambers mounted on Scanpor tape for 48 h to non-irritated, non-abraded, or tape-stripped skin of the upper back for 48 h; the evaluation of the test reaction is done after 48 and 72 h using the ETFAD reading key, assessing erythema as well as number and distribution pattern of the papules. The APT may reveal type IV sensitization in patients who are negative for the respective type I tests. Limited availability of the expensive test substances and limited reimbursement is among the factors restricting the routine use of the APT.

Food allergy-related paediatric constipation: the usefulness of atopy patch test

The aims of this study were to evaluate the implication of food allergy as a cause of paediatric constipation and to determine the diet period needed to tolerate the constipation-causing foods. Fifty-four children aged 6 months to 14 years (median, 42 months) suffering from chronic constipation (without anatomic abnormalities, cοeliac disease or hypothyroidism), unresponsive to a 3-month laxative therapy, were prospectively evaluated. All participants were evaluated for allergy to cow's milk, egg, wheat, rice, corn, potato, chicken, beef and soy, using skin tests (SPT), serum specific IgE and atopy patch test (APT). A withdrawal of the APT-positive foods was instructed. Thirty-two children had positive APT; 15 were positive to one; six, to two and 11, to three or more food allergens, wheat and egg being the commonest. After withdrawing the APT-positive foods for an 8-week period, constipation had improved in 28/32 children, but a relapse of constipation was noticed after an oral food challenge, so they continued the elimination diet. Tolerance to food allergens was achieved in only 6/28 after 6 months, compared to 25/28 after 12 months and to all after a 2-year-long elimination. Food allergy seems to be a significant etiologic factor for chronic constipation not responding to treatment, in infants and young children. APT was found to be useful in evaluating non-IgE allergy-mediated constipation, and there was no correlation of APT with IgE detection. Tolerance was adequately achieved after 12 months of strict food allergen elimination.

EAACI/GA2LEN position paper: present status of the atopy patch test

A number of scientific reports have been published on patch tests with protein allergens performed on patients with atopic eczema (AE). Evaluation of eczematous skin lesions with an atopy patch test (APT) can be used as a diagnostic tool in characterizing patients with aeroallergen- and food-triggered AE. Indications for testing with APT, choice of allergens (aeroallergens and foods), test materials and technique, including present knowledge on sensitivity and specificity, are reviewed on the basis of available literature. This position paper also points out the need for future research on the clinical use of the APT.

Food-protein-induced enterocolitis syndrome caused by fish

INTRODUCTION

Food protein-induced enterocolitis syndrome (FPIES) occurs in infants. Typical symptoms include profuse vomiting and/or diarrhea several hours after ingestion of a given food. The disorder is a non-IgE mediated food hypersensitivity. The most frequently involved foods are milk and soy, but some cases of FPIES induced by solid foods have been described. We report 14 patients with FPIES due to fish protein.

MATERIAL AND METHODS

History and physical examination, skin prick test (SPT) with fish allergens and Anisakis simplex, prick-by-prick test with implicated fish and determination of specific IgE antibodies against fish were performed. In eight children atopy patch test (APT) were also performed. In nine patients an open oral food challenge with the implicated fish was carried out.

RESULTS

There were six boys and eight girls, aged from 9 to 12 months at diagnosis, with between two and six reactions to the offending fish proteins before the diagnosis was established. Four patients had a previous history of atopy. Presenting symptoms included diarrhea in two patients, profuse vomiting in six patients, and recurrent vomiting and subsequent diarrhea in three patients. In addition to these symptoms, associated septic appearance, apathy and lethargy were present in the remaining three patients. Onset of symptoms occurred a few minutes after fish ingestion in two patients and from 60 minutes to 6 hours in the 12 remaining patients. SPT to fish were negative in all patients. Serum food-specific IgE antibodies were negative in all patients except one. APT was positive in three patients. Open oral challenge (OC) was performed in nine infants and was positive in all. The patients were followed-up for between 1 and 7 years after diagnosis, and follow-up OC tests were performed after fish had been eliminated from the patients' diet for 3-4 years. Four patients became clinically tolerant to the causal food. Three patients currently tolerate only one type of fish (swordfish).

CONCLUSIONS

We report 14 patients with FPIES caused by fish protein. The symptoms suggest a form of cell-mediated, non-IgE mediated food hypersensitivity. The gold standard for diagnosis is OC, although caution should be exercised in infants with several reactions or a recent diagnosis. After a period of elimination of the causal food from the diet, tolerance can develop.

Proposal for a standardized interpretation of the atopy patch test in children with atopic dermatitis and suspected food allergy

The interpretation of the atopy patch test (APT) to foods is not standardized. This study aimed to validate the reading of the APT in terms of the diagnostic accuracy of individual skin signs. Eighty-seven children (mean age 2.4 +/- 2.5 yr, range 0.5-13.5; 57 male) with atopic dermatitis (AD) and suspected food allergies underwent APT to cow's milk, hen's egg, wheat and soy. Twelve-millimetre Finn chambers were applied for 48 h, and results were read after 48 and 72 h. Skin changes were graded for erythema, induration, papule formation and 'crescendo' phenomenon (increase of skin sign severity from 48 to 72 h). Food allergy was assessed by double blind, placebo-controlled food challenges (DBPCFC). Sensitivity, specificity and predictive values were calculated for each skin signs in relation to challenge outcome. Of 165 DBPCFC children, 75 (45%) were positive. The combination of any skin induration plus papules (seven or more), or of moderate erythema plus any induration plus seven or more papules had a positive predictive value (PPV) and specificity for the challenge outcome of 100%; however, the sensitivity was low (8% and 15%). The best diagnostic accuracy for single signs was found for induration beyond the Finn chamber margin (PPV 88%, specificity 99%, sensitivity 9%) and presence of at least seven papules (PPV 80%, specificity 96% sensitivity 21%). Presence of both induration and of at least seven papules at 72 h were the APT skin signs with the greatest diagnostic accuracy for food allergy in children with AD.

Skin localization of cow's milk proteins delivered by a new ready-to-use atopy patch test

PURPOSE

Atopy patch tests (APTs) allow the detection of delayed allergies at the skin level. The localization of beta-lactoglobulin delivered into the skin by an innovative ready-to-use APT (E-patch was investigated and the efficacy and safety of this device were assessed.

METHODS

The E-patch containing beta-lactoglobulin was placed for 24 h in contact with hairless rat skin mounted in a Franz diffusion cell. Transdermal passage was monitored by measurement of beta-lactoglobulin A-[methyl-(14)C] or by two-site enzyme immunoassay. An iterative skin stripping allowed measurement of the beta-lactoglobulin penetrating the first external skin layers.

RESULTS

After 24 h, 92% of beta-lactoglobulin remained on the skin. The iterative skin strippings showed a 135-fold higher concentration of beta-lactoglobulin in the stratum corneum than that found in the epidermis-dermis. Analysis of the solution in the receiver compartment by radioactivity assays or immunoassays indicates that intact protein did not cross the skin.

CONCLUSIONS

The E-patch system allows native beta-lactoglobulin to concentrate in the stratum corneum, in the vicinity of immunological cells, but does not lead to its systemic delivery. Therefore, it is suggested that this delivery system creates ideal conditions for promoting a positive topical response with reduced risk of systemic anaphylactic reactions caused by the native form of the beta-lactoglobulin A.

Lessons from atopy patch testing in atopic dermatitis

The exposure of atopic eczema (AE) patients to their relevant protein allergens (eg, from house dust mite, cat dander, grass pollen, or food allergens) can trigger an exacerbation or maintain the disease. Diagnostic procedures are needed to specify allergen avoidance recommendations for the individual patient. Skin prick tests and specific serum IgE tests might be helpful in pointing out potential trigger factors, but relevance needs to be confirmed (eg, with food provocation tests). The atopy patch test (APT) involves the epicutaneous application of intact protein allergens in a diagnostic patch test setting with an evaluation of the induced eczematous skin lesions after 24 to 72 hours. The APT targets the cellular component of AE and helps round out the AE test spectrum. As a number of apparently minor test modifications greatly influence the sensitivity, specificity, and reproducibility of the APT, the European Task Force on Atopic Dermatitis (ETFAD) has developed a standardized APT technique. It consists of purified allergen preparations in petrolatum, applied in 12-mm diameter Finn chambers mounted on Scanpor tape to non-irritated, non-abraded, or tape-stripped skin of the upper back. The APT is read at 48 and 72 hours according to the test criteria and reading key of the ETFAD for appearance of erythema, and number and distribution pattern of the papules. In contrast with skin prick tests, the APT might even detect a relevant sensitization in the absence of specific IgE. Many studies have been undertaken to objectify the sensitivity and specificity of the APT to show its diagnostic use in clinical practice.

The use of patch testing in the diagnosis of food allergy

Diagnosing food allergies can be challenging to the practitioner. Our armamentarium includes standardized skin prick testing, radioallergoimmunosorbent (RAST) testing, and food challenges. These methods have certainly been helpful in the IgE-mediated disorders, including urticaria and anaphylaxis. However, diagnosing patients who have the non-IgE (cell-mediated) or mixed (IgE and cell-mediated) disorders remains challenging with our current diagnostic methods. Recent studies have examined the use of patch testing for these food-allergic patients, specifically those with atopic dermatitis and eosinophilic esophagitis. In this article, we review literature regarding patch testing: its methods, its statistical usefulness, and its potential future role.