The only way to truly diagnose a food allergy is to conduct an oral food challenge. During this test, a patient eats the food he or she may be allergic to slowly and in gradually progressive amounts while under strict supervision in a medical setting. A double-blind placebo-controlled food challenge is the true gold standard for food allergy diagnosis.2 In this type of food challenge, the patient consumes either a placebo or the food allergen separately, usually in two separate appointments. Since the allergen and the placebo look the same, neither the doctor nor the patient knows what the patient is consuming until after the challenge is completed.
Since double-blind placebo-controlled food challenges are time and labor intensive, most often providers opt for open food challenges. In an open food challenge, the patient and the doctor both know that the patient is consuming the allergen.
It’s important to note that oral food challenges are time-consuming, expensive, and potentially risky for patients.2 After all, the goal of the test is to confirm whether a patient reacts to a certain food. That means that as the food being tested is ingested in progressive amounts, an allergic reaction is possible—which is why it’s done under supervision and in a healthcare provider's office. If a meal-sized portion of the food is ingested and there are no symptoms, the patient is discharged after a few hours of observation. On the other hand, if an allergic reaction occurs, the feeding is stopped, and medication is administered as needed. The patient then continues to be observed until the symptoms go away.
Because of the drawbacks associated with oral food challenges, researchers developed a more specific form of sIgE blood test that can help healthcare providers make a more complete allergy diagnosis and better determine whether someone should avoid a food altogether or go ahead with an oral food challenge.3 This new diagnostic tool, called allergen component testing, can pinpoint the specific proteins that may be causing food allergy symptoms. That is important because not all allergies to the same food are the same, and in fact, two people with an allergy to the same food may be able to manage their allergy differently. (For more details, learn how component testing can significantly improve the way egg and milk allergies are managed.)
Ultimately, current research suggests that patients may need a combination of skin-prick testing and sIgE blood testing (both whole allergen and components) to fully understand their food allergies.3 And because allergies can change over time, patients should always follow up with their healthcare providers to see what additional testing, if any, is appropriate for them.