Food allergy and eosinophilic esophagitis: Learning what to avoid
ABSTRACTFood allergies have increased in prevalence significantly in the past decade and so, apparently, has eosinophilic esophagitis. Although the cause of eosinophilic esophagitis is unknown, allergic responses including food allergies have been implicated. This article reviews both conditions, focusing on how to detect and manage them.
KEY POINTS
- Food allergies can be classified as mediated by immunoglobulin E (IgE-mediated), non-IgE-mediated, or mixed. Their clinical presentation can vary from life-threatening anaphylaxis in IgE-mediated reactions to chronic, delayed symptoms as seen in eosinophilic esophagitis (a mixed reaction).
- The diagnosis of an IgE-mediated food allergy is made by taking a complete history and performing directed testing—skin-prick testing or measurement of foodspecific IgE levels in the serum, or both.
- Despite promising developments, food allergies continue to be treated primarily by telling patients to avoid allergens and to initiate therapy if ingestion occurs.
- Because most patients with eosinophilic esophagitis have a strong history of atopic disease and respond to allergen-free diets, a complete evaluation by a specialist in allergy and immunology is recommended.
Studies in adults
Fewer studies of the link between food allergy and eosinophilic esophagitis have been done in adults.
In a preliminary study, 18 adults followed the six-food elimination diet. Symptoms improved in 17 (94%), and histologic findings improved in 14 (78%).52
On the other hand, in six adult patients with eosinophilic esophagitis, Simon et al53 found that only one had improvement in symptoms after eliminating wheat and rye from the diet, and none had significant changes in the number of eosinophils in the esophagus.
In a 37-year-old man with eosinophilic esophagitis, symptoms improved after eliminating egg from his diet.54
Yamazaki et al55 measured expression of interleukin 5 and interleukin 13 in 15 adult patients with eosinophilic esophagitis. Food and aeroallergens that included milk, soy, dust mite, ragweed, and Aspergillus induced significantly more interleukin 5 production in these patients than in atopic controls, suggesting that both foods and aeroallergens may have a role in the pathogenesis of eosinophilic esophagitis in adults.
How to identify potential food triggers of eosinophilic esophagitis
Though elemental diets have been associated with a decrease in symptoms and esophageal eosinophilia, elemental formulas are expensive and unpalatable and pose a risk of nutritional deprivation. Identifying specific food allergens to eliminate from the diet in patients with eosinophilic esophagitis may be less expensive and more desirable than a very limited or elemental diet.
However, potential food triggers have been hard to identify in eosinophilic esophagitis. A recent consensus report did not recommend in vitro food allergy testing,37 owing to a lack of positive or negative predictive values for food-specific IgE level testing in eosinophilic esophagitis. Furthermore, the absence of IgE does not eliminate a food as a potential trigger, since non-IgE mechanisms may play a role.
Skin-prick testing is one of the currently validated diagnostic methods. Several studies have used skin-prick testing of foods in patients with eosinophilic esophagitis. In these studies, approximately two-thirds of patients had positive test reactions to at least one food, most often to common food allergens such as cow’s milk, egg, soy, wheat, and peanut, but also to rye, beef, and bean.37 In a recent article,56 81% of adult patients with eosinophilic esophagitis had one or more allergens identified by skin-prick testing, and 50% of the patients tested positive for one or more food allergens.
Atopy patch testing. The combination of skin-prick testing and atopy patch testing may be more effective than skin-prick testing alone in identifying potential food triggers. Atopy patch testing has been used in the diagnosis of non-IgE cell-mediated (delayed) immune responses, in which T cells may play a significant role.
Atopy patch testing is similar to patch testing for contact dermatitis. It involves placing a small quantity of food on the skin and evaluating for a local delayed reaction after a set time.
In two studies,50,57 146 children with biopsy-proven eosinophilic esophagitis had foods eliminated from the diet on the basis of positive skin-prick tests and atopy patch tests. Approximately 77% of the children had significant reduction of esophageal eosinophils in biopsy specimens (from 20 per high-power field to 1.1). The foods most commonly implicated by skin-prick testing were cow’s milk, egg, wheat, peanut, shellfish, peas, beef, fish, rye, and tomato; those identified by atopy patch testing were cow’s milk, egg, wheat, corn, beef, milk, soy, rye, chicken, oats, and potato. The combination of both types of testing had a negative predictive value of 88% to 100% for all foods except milk, while the positive predictive value was greater than 74% for the most common foods causing eosinophilic esophagitis.58
Though atopy patch testing shows some usefulness in identifying foods that may elicit non-IgE-mediated reactions, currently these tests are not validated and have been evaluated in only a small number of studies. Currently, no standardized testing materials, methods of application, or interpretation of results exist, and no studies have included a control population to validate atopy patch testing. More studies are needed to validate atopy patch testing as a reliable diagnostic tool before it can be recommended as a component of routine diagnostic evaluation in patients with eosinophilic esophagitis.
