What You Need to Know About Oral Food Challenges

Top Tips from Dr. Adelle Atkinson of SickKids

by: Alex Thom
oral challenges for allergy testing

Food allergies are confusing. Ask anyone who deals with them, and you'll find that answers vary from patient to patient and doctor to doctor. What we thought were facts have been proven false, and knowledge changes so rapidly, it's hard to stay on top of things. So I went straight to one of the foremost allergy experts for information about oral "food challenges" (OFCs). Dr. Adelle Atkinson is a clinical immunologist in the Division of Immunology and Allergy at SickKids Hospital, and she's also the mom of an allergic kid. In my previous conversation with Dr. Atkinson, we talked about how SickKids is working to eliminate allergies, and one of the steps in that process is giving kids accurate diagnoses.

I love that Dr. Atkinson works so hard promoting accurate diagnoses and testing, and all the things that push us to knowledge (instead of assumptions, as is the case for kids like my own son). In May 2015, Dr. Atkinson wrote a compelling piece for the Globe & Mail discussing the issues surrounding allergy misdiagnoses, and how she and her colleagues work to "de-label" kids. Considering that food allergies affect approximately 5% of Canadian kids, there are a lot of them out there who may be ready to be de-labelled, now that there is more understanding about the accuracy of allergy testing. 

In my son's case, he was born with multiple food allergies, which were confirmed mostly by reactions, and then skin prick testing at nine months of age. But five years ago, parents were told to avoid the top allergens until at least one year of age (and sometimes up to three years!), so he was never fed nuts or peanuts. He later had skin prick tests that confirmed peanut and tree nut sensitivity. The thing is, though, that he has since (accidentally!) eaten peanuts and almonds and hasn't had a reaction. If he's allergic, how can that be possible? 

His skin and blood tests still place him in the "positive" category for a peanut allergy, but his most recent ones seem to show that he may not be allergic to almonds. So, we need to do more digging. I'm going to be pressing for a referral to SickKids for oral food challenges so we can know for sure. I feel like a proper diagnosis is very important with this stuff, don't you? I mean, we could be living in fear every single day for no reason. Wouldn't it be nice to just know?

I have a lot of questions about oral food challenges, and knew many of you would, too. So I polled my readers, and fans of my Irritated by Allergies Facebook page, and posed these questions to Dr. Atkinson. 

Who is a good candidate for an oral "food challenge"?
This is done on a case-by-case basis. Skin prick tests are only about 50% accurate when they are positive, and blood test numbers mean something, but not everything. Dr. Atkinson says that a child's "story" matters, and needs to also be taken into consideration. Since an oral food challenge is the most accurate way to diagnose an allergy, previous exposures matter. In my son's case, we believe he was exposed to peanut butter without an issue, despite having positive skin and blood tests. 

A lot has changed in the last 3-5 years, so she recommends speaking to your allergist about the options.

Why should someone undergo an OFC?
There are many kids out there living with food allergy diagnoses but they may not be truly allergic. It's important to know for sure if they're allergic, and OFCs are the most accurate way to diagnose. There are, of course, many restrictions to the testing, Dr. Atkinson notes, and some patients would be too high-risk, for example, depending on the history of their reaction. But many are not! Many of the kids they see in Dr. Atkinson's clinic have positive skin tests. As mentioned, skin prick tests are a 50-50 guess, and a large hive doesn't always mean a severe reaction; there is no real data to back up the claim that a small hive would mean a minor reaction, or vice versa. It's all based on probabilities, but "probably" isn't good enough when diagnosing allergies, which is why Dr. Atkinson and her colleagues take the time to learn about patients' whole histories before undergoing testing and making a decision as to whether an oral food challenge is the way to go.

The problem with blood test results is that the thresholds are different for different foods. What's considered "high" probability for a peanut allergy (>2.0), is not the same for other foods. For wheat, nobody is certain of the cutoff -- there is a deeper understanding of allergies like dairy, eggs and peanuts, says Dr. Atkinson. There is no universal cutoff point. Clear as mud, isn't it? If skin and blood tests were accurate enough, we wouldn't need oral food challenges.

Dr. Atkinson noted that even though many patients have positive skin tests when they come to see her, many pass the oral food challenges. As Dr. Atkinson noted in her article, "Severe allergic reactions are unfortunately on the rise -- over the past 15 years, there's been an approximate 18-per-cent increase. With increased information on the prevention of allergies in children, as well as thoughtful testing, resulting in de-labelling, the hope is to reduce the incidence of food allergy over time and decrease the stress and worry for all families."

Isn't that hopeful? I think so! I can't remember what it's like to live life without the fear of anaphylaxis.

And now for the nitty gritty questions . . .

What happens at an oral food challenge?
A full history of the child's reactions, exposures and tests is recorded. The staff spend a lot of time talking and reassuring patients and caregivers about the process, too.  The information obtained from the history, skin tests and blood tests are pulled together to decide on whether an oral food challenge is the right next step.

To start, a small amount of the food is touched to the inside of the child's lips. The staff watch and wait -- is there a reaction? Any tingling? For something like peanut butter, the next step to rubbing the small amount on the lip could be 1/4tsp of peanut butter, eaten. In between each "dose" of the food, the patient is checked over, blood pressure taken, and a visual inspection for hives, swelling, etc. Dr. Atkinson says the goal (in the case of peanut butter) would be to work up to the equivalent of about two peanut butter cups. This would greatly alleviate the fear of an accidental exposure, wouldn't it?

After the final step, the patient is watched for another hour in the clinic. If there's no reaction, they're sent home, with instructions to keep an eye on the patient, and be in touch with the allergy division if any symptoms develop that they feel may be related to the challenge. 

How often do patients have reactions during OFCs?
Dr. Atkinson says they do see some children having reactions, but most are mild -- less than a handful per year would be considered severe, and they see a lot of kids. The care taken when deciding if a patient is a good candidate is why there are so few severe reactions.

What happens if there's a reaction?
Tests would be stopped immediately, symptoms would be assessed and treated if appropriate, and ultimately the patient would simply go back to avoiding the food. Since Dr. Atkinson's clinic is right in SickKids, they're in the perfect spot in case of emergencies (which, again, are rare!).

How can a parent prepare a child (without scaring them or lying to them) for an OFC?
Be honest, and use age-appropriate information, says Dr. Atkinson. Be calm when explaining the process, and be positive. This is a good thing! Dr. Atkinson really emphasizes the potential freedom when de-labelled. I honestly think I'll cry if we ever get to this point. 

How long does an OFC take?
It's a many hours long process, so plan to spend the day at the clinic. They certainly don't rush through anything. Bring lots to do!

If there is no reaction, what does that mean? 

If there's no reaction in the clinic, patients are sent home and told to avoid the food, and watch for symptoms over the next 24 hours. If they're fine after that time, they're told to eat the food regularly (3 times per week) on an ongoing basis, to ensure no re-sensitization from avoidance.

I admit that the idea of feeding my son foods we've been avoiding for the past five years scares me more than just a little, but the fact that we suspect he's had exposures with no reactions also gives me hope that maybe, just maybe, he isn't allergic. I am definitely going to request a referral for oral food challenges.

Have you been through this process? Do you think your child is a good candidate for an oral food challenge?

 RELATED: What It's Like To Live With Severe Allergies