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Oral Food Challenges: The Most Important Test in Diagnosing Food Allergy

February 25, 2020
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I routinely hear the same question from pediatricians, parents, friends, and acquaintances: Why are we seeing so many more kids develop food allergies now compared with 10 or 20 years ago? Unfortunately, there is no single answer as to why the prevalence of food allergies has doubled among children over the past two decades. Food allergies currently affect 5-8% of children and can dramatically impact their family by increasing anxiety and decreasing quality of life.

An immunoglobulin E (IgE)-mediated food allergy will cause rapid onset and reproducible symptoms with every ingestion. Common symptoms include itching, hives, swelling, vomiting and wheezing. Symptoms can vary over time and can progress towards life-threatening anaphylaxis. Some children are exquisitely sensitive and will react to ingestion of trace particles found through cross contamination of food, whereas others have a higher threshold. Adding to the anxiety these families face, there are no easy tests to determine which child is at risk for reacting to trace amounts compared with those who may not have to worry about the same exposures.

Given the many challenges associated with food allergies, proper diagnosis is paramount. Unfortunately, readily available skin prick and blood tests have limitations. Neither of these tests are in and of themselves diagnostic for food allergy. They both have high rates of false positive results and cannot be used to determine the severity of future reactions. Both skin prick and blood allergy tests should only be utilized when the clinical history is suggestive for IgE-mediated food allergy reactions. The results from skin prick and blood tests can only be interpreted according to the pretest probability deciphered from the clinical history.

The single best test to diagnose food allergy is ingestion.

A thorough clinical history can elicit important details such as the suspected food, timing of onset, as well as the character and duration of symptoms. However, when the history and/or allergy test results are indeterminate, oral food challenges are safe and the most effective way to accurately diagnosis food allergy. Oral food challenges may also be utilized as follows:

  • To determine if someone with known food allergy has naturally developed tolerance over time.
  • To expand dietary options for someone with multiple restrictions
  • To determine acute risk when food is eliminated for chronic conditions such as atopic dermatitis
  • To try to determine threshold levels

Oral food challenges take about 3-4 hours to complete. Incremental amounts of food are given every 10-15 minutes under close supervision. The goal is to have each person ingest 6-10 grams of protein, or roughly 1-2 servings. A physician or nurse practitioner is available throughout the testing, and any reported symptoms are carefully evaluated. Antihistamines need to be discontinued 5 days prior, and the challenge may be postponed if the patient is acutely ill that day – especially if they have a febrile illness or any asthma symptoms.

At Nationwide Children’s Hospital, the nine allergists and two nurse practitioners in the Division of Allergy and Immunology conducted 592 oral food challenges in 2019. We recognize the dramatic impact these visits have on family’s lives. If no symptoms occur, then that food can be incorporated into the diet without restrictions. Even if symptoms do occur, families learn valuable information including true allergic potential, what a reaction looks like and how rapidly symptoms improve with proper treatment. Many of us feel that this is the most rewarding aspect to our jobs.  

Through our experience, we also recognize how anxiety provoking an oral food challenge can be for families. We address this with every family when initially discussing the idea of an oral food challenge and throughout the day of the challenge. We have child life specialists available to help with distraction techniques and have an effective partnership with psychology services to help families utilize cognitive behavioral therapy when extreme anxiety is present. By preemptively addressing the important psychosocial impact of an oral food challenge, we try to make this a rewarding experience for every family.

As part of our effort to help as many families as possible, we are proud to announce the creation of a Food Allergy Treatment Center, which will be in Lewis Center at the Nationwide Children’s Hospital facility. We expect to start seeing patients in the new center after construction is completed in early 2021. In addition to expanding our ability to offer more oral food challenges, we will grow our psychosocial support and dietitian services, continue to evaluate new patient referrals and see follow up patients, and start offering immunotherapy treatment options.

 

Photo credit: iStock