Why are allergy tests generally not used to choose an EoE elimination diet?

Skin, blood and patch allergy tests generally cannot identify which foods trigger eosinophilic esophagitis (EoE). Their results can be difficult to interpret for EoE, so clinicians often use an empiric elimination diet and discuss treatment options with the patient and family.

The tests measure a different kind of response

Skin prick and blood tests can measure signs of IgE sensitization to allergens. UNC Health describes skin prick testing as placing a drop of allergen on the skin and gently scratching it. Allergy & Asthma Network says blood tests can measure overall or specific IgE, and some tests measure IgE to components of an allergen.

Those measurements can inform evaluation of IgE-mediated allergy, but they do not reliably identify EoE food triggers. A review in Nutrients says conventional allergy testing is not recommended for that purpose. Allergy & Asthma Network also says skin, blood and patch tests for EoE triggers are difficult to interpret.

A positive result is not proof that a food causes symptoms

A review in Frontiers in Allergy explains that skin prick tests and specific IgE tests cannot reliably distinguish sensitization from clinical food allergy. The tests' relatively low specificity can produce false positives, especially in people with high levels of atopy. A positive result therefore needs to be understood in the context of the question being asked.

For EoE, a test result alone does not establish that a food is driving the condition. Allergy & Asthma Network says tests used to identify EoE trigger foods do not always match symptoms. A broad panel may flag foods without showing which ones are relevant to EoE. In a CSACI podcast, allergist Stukus says IgE tests were not developed as screening tests and should not be used as panels.

Empiric elimination is a common starting point

Dietitian Dunn describes an empiric elimination diet as a usual first step for identifying EoE food triggers. She describes six-food and four-food approaches. These diets use a set food-removal plan rather than relying on allergy test results to select foods.

A review in Nutrients says reintroducing a trigger food can lead to relapse, making long-term adherence important. That means dietary treatment involves considering how a plan can be sustained. In an Allergy & Asthma Network webinar, allergist Lieberman says shared decision-making from the outset can include a proton pump inhibitor, swallowed topical steroids, diet or a biologic.

Testing can have a separate role

Not using allergy tests to choose an EoE diet does not mean testing cannot address another clinical question. Allergy & Asthma Network says blood IgE testing is often used when skin conditions or medications prevent skin testing. The result should be interpreted for the question it was ordered to address, since IgE test values alone do not identify EoE triggers.

In a CSACI podcast, allergist Aceves describes testing for milk, wheat, egg and soy and using the information "backwards." If a patient goes on a diet and has a large positive test, she may use that result to prompt an oral food challenge in case tolerance has been lost. That is different from using the test to choose which foods to eliminate. Patients and families can discuss the purpose of any proposed test and treatment plan with their own doctor.

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