Atopy patch test in the diagnosis of food-aggravated atopic dermatitis in adults in tertiary care

Abstract

Food allergy and atopic dermatitis often co-exist. Symptoms can include IgE mediated reactions with immediate flushing, urticaria and angioedema to delayed T-cell mediated flares of eczema or a combination of both. Existing workup for food allergy in atopic dermatitis is currently based on clinical history, skin prick tests (SPT), or specific Ig E, followed by an elimination diet and/or standardized oral food challenge. The aim of this study is to evaluate the type of food allergy and the value of food atopy patch tests (APT) in the diagnosis of food allergy in adult patients with atopic dermatitis. We recruited 11 adult patients (3 Male, 8 Female) aged 26-47 years with atopic dermatitis (as per Hannifin and Rajka criteria). All patients kept detailed food diaries and symptoms correlation with questionnaires. They also had blood test specific Ig E, SPT and food APT. If positive, they were advised on a food elimination diet. They were followed up with at least 3 clinic visits over a course of 8-16 months. The results of these investigations were then correlated with their symptoms. Seafood including shrimp (n=8/11, 73%), lobster (n=8/11, 73%), crab (n=7/11, 64%), clam (n=6/11, 55%), and oyster (n=5/11, 46%) were the most perceived culpable food allergens based on the food diaries. The type of symptoms reported ranged from pruritus (n=10/11, 91%), wheals (n=5/11, 46%), flushing (n=5/11, 46%) and eczema flares (n=6/11, 55%). The most commonly observed reaction was that of pruritus, typically experienced within 1 hour of ingestion. Positive symptom correlation with elevated food-specific IgE levels were seen with shrimp (n=3/8, 38%), lobster (n= 2/7, 29%) and crab (n=1/7, 15%). Clinical correlation with positive SPTs were seen with oyster (n=1/6, 17%) and crab (n=1/6, 17%). Positive results across all 3 modalities of specific IgE, SPT and APT was noted with shrimp (n=1/8, 13%). Food APTs were negative for the other allergens. All patients reported improvement in their symptoms after trial of food elimination diet. 1 patient sustained an adverse reaction, he developed an angry back after APT. Seafood, in particular crustacean seafood is a common food allergy seen in adult patients in Singapore. In our small pilot study, food atopy patch test is not useful as a tool for diagnosing food allergy in adult patients with atopic dermatitis. We still need to rely on correlation with clinical history, specific Ig E, SPT, elimination diet +/- oral food challenge.