Ep. 292: Food Allergy Testing, Diagnosis, and When to Food Challenge

Diagnosing a food allergy isn't always as straightforward as it may seem. Was it really the food? Which food caused the reaction? And how do allergists put all the pieces together to arrive at the right diagnosis?

In this episode, we're joined by FAACT Medical Advisory Board member, Dr. David Fleischer, to take us behind the scenes of the diagnostic process. We'll explore the different testing options allergists use, how they determine whether someone truly has a food allergy, and the important role oral food challenges play—including when it's time to consider one.

Resources to keep you in the know:

• Oral Food Challenges 
• Accurately Diagnosing and Managing a Food Allergy
• Newly Diagnosed

You can find FAACT's Roundtable Podcast on Apple Podcasts, Pandora, Spotify, Podbay, iHeart Radio, or wherever you listen to podcasts.

Follow us on Facebook, Instagram, BlueSky, Threads, LinkedIn, Pinterest, TikTok, and YouTube.

Sponsored by: Genentech

Thanks for listening! FAACT invites you to discover more exciting food allergy resources at FoodAllergyAwareness.org!

Transcript

Caroline: Welcome to FAACT's Roundtable, a podcast dedicated to navigating life with food allergies across the lifespan. Presented in a welcoming format with interviews and open discussions,

each episode will explore a specific topic, leaving you with the facts to know or use.

Information presented via this podcast is educational and not intended to provide individual medical advice.

Please consult with your personal board certified allergist or healthcare providers for advice specific to your situation.

Hi everyone, I'm Caroline Moassessi and I am your host for the FAACT Roundtable podcast. I am a food allergy parent and advocate and the founder of the Grateful Foodie blog.

And I am FAACT's Vice President of Community Relations.

Before we start today's podcast, we would like to take a moment to thank Genentech for being a kind sponsor of FAACT's roundtable podcast.

Also, please note that today's guest was not paid by or sponsored by Genentech to participate in this specific podcast.

In this episode, we're joined by FAACT Medical Advisory Board member and allergist, Dr. David Fleischer to take us behind the scenes of the diagnostic process.

We'll explore different testing options allergists use,

how they determine whether someone truly has a food allergy, and the important role of the oral food challenge,

including when it's time to consider one.

Welcome back, Dr. Fleischer, to FAACT's Roundtable podcast. We are so happy you're here. This is a really important topic because I think sometimes we forget the basics and then we forget how to continue.

So this is going to be an amazing conversation.

Dr. Fleischer: Thank you. I look forward to it. It's an honor to be here. Thank you for having me.

Caroline: Well, thank you. We appreciate you very much and your work.

Dr. Fleischer: I love what I do, so it's easy, easy to do those things when you love what you do.

Caroline: So you know, that's what you hope everyone can say in life, right? I really love what I do, but it shows, you know, because again, you're just like today, you're participating in a podcast to educate the community.

You just go above and beyond. And that's what we're going talk about actually is about you right now for a quick second. So before we dive into today's topic, we'd love our listeners to get to know you.

So can you share your journey as an allergist, a researcher? You're an advocate too.

And what inspired you to dedicate your career to advancing food allergy care?

Dr. Fleischer: Yeah, well, I was a poster child probably for allergy when I grew up. So I grew up with pretty severe asthma. I was in the hospital probably a dozen times with asthma.

Had horrible seasonal allergies in Florida growing up and had allergy shots and eczema and,

and all those things. I really got close to my pediatrician and my, my allergist and I really was curious about medicine probably before high school. So I, I kind of grew up in the medical arena, just be with all my illnesses and it was a logical field to go into medicine.

I really love what my doctors did,

respected it. I just, I knew that I wanted to be a doctor very early on. And then I, you know, I went through med school and residency and I thought I wanted to do asthma research, but luckily I had a very strong mentor, very convincing mentor to say, you don't see it right now,

but food allergy is going to be the future of allergy, so you need to do that. So Bob Wood was my mentor at Johns Hopkins and he, he really set me on the path to food allergy.

And I did several big studies with peanut and tree nut allergies at Johns Hopkins during my fellowship.

Really fell in love with food allergy at that point. So that's really what got me interested, was shifting from what I thought I wanted to do. Luckily, somebody smarter than me seeing the future for me.

Food allergy for me is fun. It's probably one of the hardest things to treat, I think, for families these days and the impact on the whole quality of life for the whole family.

But the challenges and those things really get me motivated to try to help families. In the studies and research that I've done, natural history studies and primarily treatment studies, really has guided me into the person that I am today as a food allergist.

Caroline: I love the. Bob woods influenced you. That is so exciting.

Dr. Fleischer: He really set me on the path and like I said, I've had some great mentors along the way that have really said you just,

you're not. You got to look beyond some certain things, you know, and trust me that this is going to be the field that you're going to want to get into.

And,

and it just became fun for me. I mean, the research was, was fun. I love the combination of seeing patients and doing research and helping families in multiple ways.

Caroline: So that's exciting and I'm glad you chose us and listeners. Bob woods is like one of the OG Allergists.

Dr. Fleischer: Yeah. Out there, godfathers of food allergy. So it's, it's,

you know, to be in that lineage from him and all the people that he used to mentor across the years, it's, it's really impressive. Over almost 40 years, really, they've had this training grant where they've trained academicians around, around the country in the world.

So it's.

I was privileged and lucky. I mean, I worked hard, don't get me wrong, to get where I got. But it was, there was some luck, I'm sure, along the way, too, and good fortune.

But it's, it's been such an amazing journey and it's, it's still continuing. So it's just like, again, I love what I do and if when it's fun, it doesn't feel like work.

Right. So it just,

it's great. So it's, it's really a fun field to be in and, and, you know, to be supported, to be an advocate as well for food allergy with FACT and other organizations.

I think, you know, it's, it's the whole package which just really makes things really feel good about what we're, what we're doing with food allergy. So.

Caroline: Oh, you just said it perfectly. It feels good. It just feels so right,

you know, And I'm a parent of two children, adult children with food allergies. And it just feels so good to see how this area has change and grown and to see people like you and Dr.

Woods and different people that have just changed our world completely.

Dr. Fleischer: Like I said, it's an honor and privilege to be able to see patients as a physician and be able to do research and advocacy and other things. It just, it rarely makes it a pleasure to get up in the morning and go to work and do the work and do these things like we're doing today.

Caroline: So thank you. We really appreciate you. And so turning to our topic.

Dr. Fleischer: Thank you.

Caroline: Diagnosing a food allergy is a bit like solving a mystery.

Can you walk us through how allergists gather clues from patient history to testing to arrive at the right diagnosis?

Dr. Fleischer: It's an excellent question.

Saying you're a detective is exactly the right word. You're an investigator figuring out what happened with the food. So clinical history is the most important piece of information that you can get from a patient with food allergy.

What we teach the residents and med students and fellows is really, you are an investigator here. You've got to get a clear history of what the exact foods were, how they were cooked, how were they prepared, were they contaminated with anything else,

the timing of the introduction of that food and the relation to the reaction. Because for IgE reactions, we know they happen within two hours.

So getting that. So, for example, I had A patient the other day that ate two foods within several hours, it was a peanut,

and then two hours later ate egg and broke out with hives. But if we didn't get that history, clearly that tolerated peanut probably for two hours beforehand and then reacted to egg because the timing was consistent with the egg reaction,

it really wouldn't have come across as that clear that they were allergic to possibly both peanut and or egg. Right. So it's really getting those questions asked correctly, getting the timing,

the severity, reactions, how they were treated,

and then basing your testing on what you gather from your clinical history. Because we really don't want to do screening, let's call it screening, kind of skin testing in patients that haven't had a clinical history of a reaction,

because our tests are really meant for you had a clinical reaction to a food,

it's consistent with an ige mediated reaction within two hours with hives or swelling or other IGE symptoms.

And then you go on to testing based on that. We try not to again screen for foods that kids haven't eaten. But again, we, I think as allergists, we all do that to some degree.

So we have to just be careful how you do your testing. And the testing really is based on again, the clinical history and then using skin test, primarily because the skin test gives off answers within about 15 minutes of that appointment.

So you can leave that appointment knowing what you're probably allergic to or not. And then we use serum IGE testing, looking for antibody levels for those foods in the blood as well, which help us predict sometime when they're going to outgrow it, if they're going to outgrow it at all.

Because if the numbers are really high on those blood tests, they're not likely to outgrow it. And we use those tests also to monitor the patients over time to see are they outgrowing their allergies and when is it time to do a food challenge, for example, to see if they've outgrown it.

So again,

the biggest thing I can say is you are that detective. Like you said, you've got to get a great clinical history, ask the right question. For example, again, what kind of like with egg or milk is, are you eating in other forms, like baked forms and tolerating and those.

So again, it's teaching the residence fellows and med students and how to ask the questions, what questions to ask and then guide based on that history, your testing. Because again, you don't want to do a lot of testing in a patient that hasn't eaten the food because you can get false positive tests.

So that's. I know we're going to talk more about the tests and their reliability and what's coming and the precision of those tests. But that's the basic gist of it, is you got to ask the right questions to get the answers to guide you for your testing, that you need to confirm or refute an allergy.

Caroline: So when you mention taking history down, would you suggest to people listening today that if they have this new allergic reaction or new kind of response to a food or a lotion or just anything like that that's made from a food product, should they just immediately jot down some notes?

And if they do, what would you be looking for from those notes?

Dr. Fleischer: Absolutely, it always helps. And even taking pictures of the reactions that they had, showing us that their hives are not. Or maybe it was a benign rash, that they got some redness around the mouth.

So pictures help with documenting exactly what you ate at that point in time that you had the reaction. So exactly what foods have you eaten those foods before in other forms.

But yeah, parents, if they can write down exactly what was in those foods or have a label that they even have, that they can take a picture of and send to us or bring to us or bring the product in itself.

But knowing what they've eaten at that meal, exactly what they've eaten before, helps us immensely.

And the timing of that writing it down, because sometimes you forget how long it took and if it's been a while to get into your doctor.

So absolutely, that's a fantastic idea to write things down about those events, take pictures of the reaction so we can see the photos and. And that will help us immensely.

Caroline: That's a great idea about the photos because we all carry our phones now, which cameras on them. And so that's very helpful too, because they could just take a photo and then even put the note right into their phone section.

Dr. Fleischer: On most phones, you can just type a quick date and reaction timing what it was. All those things that we just talked about in those photos really help a lot because again, we try to distinguish, you know, other rashes from hives and things like that, so.

Exactly. I think those things are key to help us in those in the management of these patients. The more history that the parents can provide the details, the easier it makes our jobs,

which is good.

Caroline: We want that. So now let's look a little to the future and if there's any new, exciting advances coming in food allergy testing and let's talk about the different types of tests, and then really just start to dig into that, you know, about how you get to that diagnosis.

And then once they're diagnosed, then what's next?

Dr. Fleischer: Sure. I mean, right now, like I said, the main tests that we have are skin tests that give us a nice answer the same day.

You know, if you've got a clinical history that's consistent with an IG reaction, you have a positive test on the skin test that confirms the allergy,

then the serum IgE testing can be done as a marker of kind of their progression of their allergy. Because a lot of kids don't outgrow peanut and tree nut, for example.

Only 10, 20% outgrow tree nut and peanut, respectively. So if you watch those numbers over time go up on the blood test,

those are kids that aren't going to likely outgrow it. So again, following the skin test and the blood test,

not necessarily every year. It depends on the patient. If your numbers are really high on a skin test or blood test, doing tests every year probably is not necessary. But those are the main tests we have right now.

And the precision of those, I'd have to say, honestly, is not, not the best, because, again, the false positive rate is quite high. So what's coming down the pike? You know, I think there are several tests that have been helpful, such as mast cell activation or basophil activation tests.

You know, they're more easily available now. You can get them at different reference labs.

So some people use those to monitor patients that have food allergies, to see as a time to challenge them, to see if they've outgrown their allergy. We used to have the ability to do what's called some epitope mapping, which is looking at different, certain binding sites of antibodies.

And some of those early studies looking at the epitope mapping certainly seem to show that some pips, some could predict severity, some could predict who's going to outgrow it or not.

But unfortunately, the company that was doing the epitope mapping financially didn't do well. So it's. We're trying to. I know Dr. Sampson, who's worked with that epitope mapping for many, many years.

Hugh Sampson, another godfather of allergy, is trying to revamp that company, at least what they've done, because I think there were some promising things coming from epidural mapping that we'd like to be able to use.

But right now it's. It's really limited to skin test and blood tests and really food challenges that I know, we'll talk about as well. But once you're diagnosed with the food allergy, it's really,

it's management at that point. Right. And there's several different management levels. The first is obviously getting patients epinephrine auto injectors or other forms of epinephrine. Now with nasal epinephrine available,

sublingual epinephrine coming,

but having some form of epinephrine available for patients because we can't predict severity really well to any degree. So every patient we feel is at risk for severe reaction. So needs to be prepared,

have an action plan based on that epinephrine device or whatever it is, and having antihistamines appropriate for weight and things like that.

So having the action plan in the emergency medications, that's the primary. We're spoiled at children's and I think other places are spoiled too. And having dietitians, I think dietitians, I can't tout the them enough because as you remove a food, you need to be able to introduce other foods that will,

that will compensate for that in the diet. So if you remove milk, you've got to have calcium and vitamin D somehow. So you need to make sure that they're getting the nutrition that they need when they avoid these foods.

But also teach avoidance, which our dietitians do very well.

And then really the conversation I have these days is about treatment, to be honest, because I think most families these days don't want to sit around and sit on their hands doing nothing waiting for reactions to happen.

They want to be proactive and treat their kids to provide some protection basically from allergic reactions or potentially get rid of their allergies with some of these therapies. That's the longer term goal.

But most of these therapies are meant for desensitization or protection from allergic reactions. So we have initial conversations. Sometimes it's not that first conversation because it's overwhelming to be diagnosed with a food allergy.

So sometimes I'll bring them back with,

you know, a few months later and say, well, let's talk about treatment options. Let's put this in an optimistic spin because we have treatments available and if we start them early, we know they work better.

So it's a much more optimistic conversation to have with these families these days than just saying, okay, we're just going to avoid this for the rest of your life or for whatever number of years we'll retest,

see if you outgrow it. Parents don't want to sit around though. They want to Be proactive and protect their kids,

but also give them a chance to better outgrow the allergies that aren't outgrown like peanut and tree nut and seed allergies.

Caroline: So these are really exciting times. I mean, my children are 23 and soon to be 28, and back then we were told just avoid good luck.

Dr. Fleischer: But it was, it was, we'll see you back in a year or two, we'll see what your numbers are and maybe we'll consider a challenge. But if the numbers are still big or going the wrong way,

you're not going to outgrow these. And I think it doomed a lot of kids to having peanut and tree nut allergies, especially because most kids outgrow milk and egg and soy and wheat and, but most don't outgrow the seafood and the nuts and peanuts.

So it's, it's hard with those. And if I can give them a 9 out of 10 chance, potentially about growing it with some therapies or at least treating them and getting them, you know, protected from these things, most families decide that, yeah, I want to do that.

I don't want to just wait and see you in a year and see what happens, happens over the next year and see if a reaction happens or accidental exposure because those things scare families all the time.

I mean, it's just imagine being worried about your kid having a reaction. And kids eat every 2, 3 hours, except when they're sleeping.

So you're constantly worried until they're in their bed, going to bed and you know they're not eating right. So it's not easy to have a food allergic child for sure.

You know, if, if you've got food allergy these days,

there's treatment options A and B, there's a lot more things coming. The research that's going on right now and the treatments that are going on,

it's coming along and there's going to be more options for families, which is great.

Caroline: That is very exciting. And so, okay, I'm going to bring this up and I know you're going to be cringing, but we see, I know this is so terrible, but we see online in home allergy testing,

you

Dr. Fleischer: Google something in that AI or whatever it is, they, they send stuff to you because they figure you're searching for those things. There are a lot of tests that aren't good out there.

Caroline: Okay.

Dr. Fleischer: So it's called IGG testing instead of IGE testing. IGE antibodies are the dangerous ones. IGG are the good ones that you're supposed to make when you eat a food and make a protective antibody because foods are foreign proteins when you first eat them.

So either make protective ones or dangerous ones igg.

So really the IGG don't predict hypersensitivity like these tests predict. I mean you get this nice color coded kind of outline of all the foods that you've eaten and levels of IgG which are probably higher, but the foods that you eat more.

So parents are recommended to take out these foods that have high IGG levels on the things and, and those are things that they've been eating for years.

Right. So it's, it's really not good. Testing food sensitivity or food intolerance is a very hard thing that's different than allergy.

So food intolerances aren't immune mediated like IGD mediated or non IG mediated food allergy. And there's really no great tests except for lactose intolerance and some other enzymes that you can get fructose intolerance when you get biopsies done with endoscopy and things.

So parents come to us a lot of different reasons. So what's my child's abdominal pain from? What's my child's,

the adhd. There's things about avoiding gluten, does that improve symptoms and things like that, autism and avoiding certain foods. So it's very hard to diagnose those intolerance and things. And I think the tests that are out there really prey on families to get an answer.

You're looking for your son has chronic abdominal pain and you're like it's got to be a food because they eat all the time. So it's got to be a food but it's not often the food that does it.

But they're looking for answers and I think there's more and more of these tests coming out. Like I said, my wife got sent forward me a couple that she saw and I think you've got to really be careful taking foods out of a child's diet.

If you try to see if a food's bothering them like an intolerance, try it for several weeks,

see if whether symptom gets better. But if it's not, put it back in. Or if it does get better, we want to put it back in to see if it recurs the symptoms to make sure it proves that that's the problem.

But you don't want to be avoiding a ton of foods if you don't have to because it affects the clothes quality, life. But B is the nutrition and growth that we're most concerned about with these kids.

But I understand why parents look for these things because they're looking for answers for what's causing their symptoms. But you know, our tests are really meant for certain types of allergy, immune mediated things, not these other types of tests that are very expensive and often not covered by insurance and don't really help patients,

in my opinion, and cause more harm than good.

Talk to a physician or allergist before ordering some of those tests come to us to let us explain what we can test for and what we can't test for.

What tests are really reliable or not before you spend a lot of money and take a lot of foods out of someone's diet unnecessarily.

Caroline: So appreciate those wise words. And so now turning to the oral food challenge, we know that those can be absolutely life changing for some patients. So therefore can you help us understand when they're used,

what information do they provide to you and then how proactive patients could be about asking their allergist whether it's time to consider one or not.

Dr. Fleischer: Food challenges are really a key part of our management of patients with food allergy. Without them, we couldn't do food allergies. So the double blind placebo controlled food challenge is considered the gold standard for diagnosing food allergy.

That's a research challenge that we do.

Most of our challenges that we do are what are called open challenges.

And they're meant to be done for several reasons. Reasons one, to see if you've outgrown the allergy.

Sometimes they're done to prove that you have the allergy or not because the history is not clear and the testing is not clear. And sometimes it's obviously to refute food allergies.

So if you get a testing that's negative, the history is consistent, then you can use the challenge to prove that you may or may not be allergic. So they are the biggest thing, and that's why we have one of the biggest challenge units in the country at our institution,

because we do so many challenges, but because they're such a key part of what we need to do. But they are life changing. I mean, I walk through the challenge unit every day that I'm in clinic, at least while I'm there at the hospital, because it's such a joy to see the joy in the patient's faces when they,

they can actually eat the food and get rid of their allergies. Maybe they were thought they had an allergy and really they didn't because the challenge Proved that. So they, they are essential, but they come with risks and they come with expense and things like that.

So not every practice does them because of the risk of some of these challenges and just the resources that certain academic institutions or other practices may have. So it takes resources to do this, a dedicated nurse use, sometimes a dietitian to make these products and things to get the right thing.

So it takes a lot of resources and we're lucky at academic institutions that have those additional resources that maybe practices don't have. So we almost do between 2,500 and 3,000 challenges a year.

So it's a lot that we do. And if we didn't have our challenge, you know, we couldn't function without those. But they, they really are important. We use them in studies as well, the double blind ones, placebo control, to get patients into studies based on FDA requirements and things.

But the change in getting rid of an allergy is huge for families. I think we can't do what we do without challenges. When is it time to do those challenges?

That's when we use kind of the skin tests and the blood test to help help us determine when is it time to challenge like an egg patient, when is it time to challenge the scrambled egg or with milk, challenging to bake milk, things like that.

Or when is it time to see if they've outgrown peanut or tree nut allergies. So that's where the testing helps us. And that may be where some of that mast cell activation, basophil activation may give us more reassurance that they'll pass a challenge.

But again,

we don't use those clinically yet at our institution, we tend to rely on the skin and blood tests to determine when a patient will be challenged.

Caroline: They definitely have been life changing for my kids and just the testing was indicating they might or might not still be allergic, where it was a little ambiguous. And going through that food challenge and then realizing that they're no longer allergic to something was huge.

My son was able to have baked dairy. That was crazy.

Dr. Fleischer: We do sometimes ladders too, which are kind of build up on baked products and things. I mean, just the,

the quality of life improvement that you can do with a challenge is, is just immense. I mean, like I said, if you can get some foods in their diet,

then a baked form for milk and egg and help them outgrow their allergy or just be able to eat those things makes a huge difference.

And then just getting things off their list. I mean, I, I saw,

you know, a seven, eight year old yesterday. And the smile on her face when I told her eggs contest was negative and she's outgrown it.

She's like, I want eggs because I don't like them, but now I can if I want to, right? And I don't have to worry about epinephrine. And the mom was like, so I don't need an epinephrine device anymore.

I'm like, no, your child's outgrown. And she's like, I never thought this day would come. Right? And it's just, it's liberating. It really is. I mean, like I said, the quality life impact for the whole family.

With food allergic patients, it's not just the patient, it's the whole family that's truly affected. Going out to restaurants, worrying about the kids,

sleepovers, all these things that we take for granted with kids without food outlets, I don't think people understand the impact that it has.

And if we can improve that quality life with challenges, we certainly will.

Caroline: So like I said, it has just been life changing for our family and we've actually come to the end of our time together. That went really, really fast.

So before we say goodbye today, is there anything else you want our listeners to hear from you?

Dr. Fleischer: I think, I think the biggest thing is optimism.

One word I can say is it's optimism. We don't feel like having food allergy is you're sentenced to life with it. These days we want to try to start these therapies often between 1 and 3 years of age because there are data showing that the younger you start, the better the therapies may work,

the safer they are. You know, the fear and distaste you have developing. But as you avoid these foods for years and years, doesn't happen.

So if I can start these kids on therapies between one and three, I can get them probably eating a lot of these foods by four or five. So by the time they're school age,

it's just a part of their diet. They never knew they had the allergy. So that's the most rewarding for me.

But we're still finding therapies for older kids too. So I think for families it really is.

Talk to your allergist. If the allergist doesn't have options for you, find another allergist that does. Because I think these treatments and are going to change how we manage food allergies.

So hopefully we'll have less food allergic adults in this world.

We get rid of every food allergy.

Caroline: No.

Dr. Fleischer: And some families will choose Avoidance or patients will choose avoidance, which is a certainly safe and practical thing to do. But I think it's like I said, as more parents come to us,

they want to be proactive and we'll have things for them.

So just be optimistic. It's not a life sentence, I don't think at this point. And let us help you get through this journey because it is,

it's a journey. I mean, the other thing is that, you know, treatments are three to five year process. It's a marathon, not a sprint. So we just have to remember that we'll get there slowly and there's more coming.

So I just encourage families to, if they don't get the answers they want,

find someone that they get an answer to and find the treatment that they want because there are good ones out there now that are safe and effective and really can change the natural history of this disease over time.

Like I said, we won't get rid of all food allergy or prevent all food allergy. But I think if we've got more treatment options and we've got good practices with testing, better testing and challenge outcomes and more people doing challenges,

we'll make these, these families a lot better over time.

Caroline: So thank you so much for your time today and imparting such wonderful wisdom. We just appreciate you and all your work so much. So thank you for being with us today.

Dr. Fleischer: It's my pleasure. So you're very welcome.

Caroline: Thank you. You're welcome.

Before we say goodbye today, I just want to take one more moment to say thank you to Genentech for their kind sponsorship of FAACT's Roundtable podcast.

Also, I want to note that today's guest was not paid by or sponsored by Genentech to participate in this specific podcast.

Thank you. Thank you for listening to FAACT's Roundtable Podcast.

Stay tuned for future episodes coming soon.

Please subscribe, leave a review and listen to our podcast on Pandora, Apple Podcasts, Spotify,

Google Podcasts, iHeartRadio and Stitcher.

Have a great day and always be kind to one another.