A component of the workup of eosinophilic esophagitis (EoE) is the allergy evaluation. A number of studies have demonstrated that allergies when children with EoE who have been placed on a diet of only a hypoallergenic elemental formula, in almost all cases they have rapid resolution of their symptoms, and normalization of their esophageal biopsies. This is strong evidence that food allergies is the main cause of this disease. There are some cases of EoE that seems to be driven by environmental allergies.
Although elemental formula diets are highly effective, they can be quite challenging to stay on, so the role of the allergist is to try to identify which food allergens may be triggering a patient’s disease so that they can be removed from the diet. There are 3 ways in which food allergies has been used in EoE.
– Skin prick testing
– Blood allergy testing (eg. RAST)
– Atopy patch testing
The first two types of allergy tests are used most commonly to look for food allergies that have caused an allergic reaction such as hives, wheezing, or anaphylaxis. They have also been used to evaluate for environmental allergies which may be triggering asthma or hay fever symptoms. Skin testing and RAST testing have in common that they detect IgE mediated allergies, that is allergic reactions that are caused by this allergy antibody typically associated with immediate-type reactions.
There are limitations with testing as these IgE-mediated tests were not developed for detecting triggers in EoE. As a result there can potentially be false positive and false negatives.
Patch testing has been proposed as another way to evaluated for food allergies. The theory is that patch testing can look for delayed non-IgE type of allergies, which is considered to be involved in the development of eosinophilic esophagitis. Patches of various foods can be placed on the skin for 48-72 hours looking for signs of inflammation at the patch test site. However patch testing for foods in EoE has not been validated; in fact most centers do not offer patch testing to foods.
The major limitation with all of the above testing is that they are not 100% accurate. Testing can not guarantee to identify food triggers in EoE and there are often false positive and negative results. Because of these inaccuracies with testing, some physicians may not perform any testing and start with empiric elimination diets avoiding the most common triggers of EoE.