269: Allergy Testing: Everything You Need To Know w/ Dr. Stacy Silvers

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I'll be direct. Anything and everything to do with food allergies seems to be kind of confusing. I'm hoping today to demystify some of the questions and thoughts and ideas from the patient side of things around allergies and allergy testing, specifically.

Today's guest, Dr. Stacy Silvers is a board-certified allergist specializing in environmental and food allergy diagnosis, treatment and prevention. Dr. Silvers oversees Aspire's allergy program and protocols, and also leads the food allergy and oral immunotherapy (OIT) program at Aspire Allergy & Sinus. Dr. Silvers is considered an expert in the field of food allergy diagnosis and treatment. Join us as Dr. Silvers discusses all things relating to food allergies, diagnosis and treatment!

What do you have experience with? Is it patch testing, skin prick, intradermal testing, blood test… the whole nine yards? Let me know in the comments what has worked for you and if your diagnosis was a game-changer!

Or, listen on your favorite app: iTunes (Apple Podcasts) | Spotify | Stitcher | TuneIn | Subscribe on Android

In this episode:

  • Food sensitivities vs. food allergies
  • The differences between allergen testing — blood, patch + skin prick
  • Which medications interfere with allergy testing results
  • Why you could develop a food allergy despite eating it before without any issue
  • Thoughts on removing foods to figure out a food allergy


“That's one of the benefits of (skin prick) testing is you get quick results, usually before you even walk out the door. So that test is very good for nasal allergies, food allergies, anaphylactic type reactions.” [05:31]

“When we compare prick testing and the lab testing, the sensitivity is about 75% with the blood test compared to the prick test. So if we can do the prick test, we prefer to go that route. But we can't always do the prick test. You have to be off certain medications in order to do the prick testing reliably.” [09:12]


Find Dr. Silvers online

Follow Aspire Allergy on Instagram

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Healthy Skin Show ep. 222: Food Allergies + Skin Rashes in Kids w/ Jennifer Brand, MS, MPH, CNS

Healthy Skin Show ep. 037: Nickel Allergy And Eczema w/ Dr. Peter Lio


269: Allergy Testing: Everything You Need To Know w/ Dr. Stacy Silvers FULL TRANSCRIPT

Jennifer: Hi, Dr. Silvers. Thank you so much for being here today.

Dr. Silvers: Oh, absolutely. Thanks for having me.

Jennifer: I am really excited to have this conversation with you, because actually, it's you and your colleague, Dr. Chris Thompson, we're actually both on the show, which is so exciting. And I'm really appreciative to have had both of you here because one of my dreams for this year has been to have a presence and hold space for people dealing with allergies and people who are also confused about allergies. Cause I think this is, to be honest with you, I think it's confusing.

Dr. Silvers: Absolutely.

Jennifer: I think most people think it's kind of confusing. So that being said, I'm hoping today to demystify some of the questions and thoughts and ideas from the more patient side of things around allergies and allergy testing, specifically. So let's start off with defining what allergies actually are. Because I feel like sometimes people use other terms. They say, “I have a food allergy.” But really they have a sensitivity and they use these interchangeably and it gets confusing. So can you set the record straight? What is an allergy?

Dr. Silvers: Yeah, you're absolutely right. I mean, allergy sometimes gets lumped into this catchall phrase, but for me as an allergist, it's a very specific definition and it means there's an immune response to something. So you are either making antibodies against things or there are immune cells that are acting against chemicals to cause your symptoms. Whereas things like sensitivities don't have that immune component. Now these foods or things you come in contact with may be causing symptoms, but it's not an immune response. So that's where the difference comes from.

Jennifer: And can I ask you, you said immune cells, what would it be an example of an immune cell that would be part of this response?

Dr. Silvers: Yeah, not to get too into the weeds, but there's certain innate immune cells that are just always there and ready to go. But what we oftentimes think about are T cells and they really drive a lot of the immune response. They're the brains behind the immune system and that's what really gets engaged in many of these disorders that we're dealing with.

Jennifer: Okay. So there is something called IgE and the IgE response, but you had shared with me that sometimes with allergies, it's not always an IgE mediated response that could be triggering a more allergic response. Could you that's explain that?

Dr. Silvers: Sure. So IgE is immunoglobulin E. This is thought of as being the bad guy for things like nasal allergies, most food allergies, anaphylactic type reactions. IgE is what drives those types of reactions. But we're dealing with things like contact dermatitis, for example, where you get some chemical on your skin and you get a rash. That is usually not IgE mediated, that is usually a cellular mediated process where these T cells are really getting activated and causing the rash that you typically find. So those reactions typically aren't as acute. They don't happen as quickly as the IgE mediated reactions and sometimes, like skin testing, that we'll talk about in a little bit, don't help a lot with those kinds of reactions either because it's a different pathway, different cells are involved.

Jennifer: Okay. That's helpful. So I will share that a long time ago I got patch test. I think it was patch testing. In fact, you know what I'm going to say, I don't know what it was. Because I've heard prick testing, patch testing. I don't know if that's the same thing?

Dr. Silvers: Nope, very different.

Jennifer: But I got things put on my back and I had one spot that drove me nuts. Turns out I am very allergic to dust mites. And now I know when I put on a pair of pants and become incredibly itchy that those pants, if they were not washed in maybe a month or so, or they sat in my closet a long time, I am going to have hives all over my legs. So can you share with us, what's the difference, what is patch versus prick testing? And then we can go into blood testing, but I think those are probably the two good spots to start.

Dr. Silvers: Absolutely. So this is a perfect segue into testing because when we're looking at prick testing, the percutaneous testing, that's when we're looking for the IgE mediated reactions. So what happens when we do this is we apply a little extract that contains whatever it is we're testing for, be that environmental like dust mite, pollens or foods. And then there's a light scratch that goes through that and just barely has that extract enter the skin. With that type of reaction, we're going to get results in the order of minutes, 15 to 20 minutes or so, because we're seeing an IgE mediated reaction. So that's one of the benefits of that type of testing is you get quick results, usually before you even walk out the door. So that test is very good for nasal allergies, food allergies, anaphylactic type reactions.

Patch testing's completely different. Patch testing is really looking for people with contact dermatitis. A good example is a nickel allergy, for example. Some people, if they have earrings that are made out of certain metals, they'll get a rash because of that. It's an immune mediated response, but it's not IgE mediated. So how do we test for that? We test with patch testing. So with this, we have little wells, these little cylinders that we fill with whatever chemical we're testing for, and you basically tape it to someone's back. But the difference here is you have to wait a good 24 to 48 hours before you can read the response because it's not acute like IgE mediated reactions are. It takes hours to days before we see something happen. So with this, the tests are usually applied. You come back two days later, take it off and see what individual spots have caused a reaction. And even then sometimes you come back an additional time, a third time, to get a final reading and go over all the results.

Jennifer: Wow. So it's a longer process for a patch test.

Dr. Silvers: It's a much longer process, yeah. And we do this more commonly with say some of our eczema patients or people who are getting rashes with certain personal hygiene products and things like that.

Jennifer: So does that imply that the frequency with which it's used plays a role or it doesn't matter. Like, if you had say used, I don't know, let's pretend I used a lipstick. And I used the lipstick, I don't know, once a week and I seem to be fine, but I'm having certain issues. I'm just trying to think about, that's so interesting, it takes time though. It's not about the amount that you're exposed to. It's more that it takes time to develop a reaction.

Dr. Silvers: So let's say you use a product once a month.

Jennifer: Okay.

Dr. Silvers: Well you apply some cosmetic. You may not get a rash after that one application for hours to a day later. It can take that long for the immune cells to get activated and cause the symptoms. Now, if you're using something on a consistent basis though, you're probably going to have that rash much more consistently.

Jennifer: Okay.

Dr. Silvers: And it may not ebb and flow much.

Jennifer: And for this particular example of the patch test, that's where it's not good for food allergies? Correct?

Dr. Silvers: Yeah, that's correct. Yeah.

Jennifer: Okay.

Dr. Silvers: Food and pollen allergies are almost tested for exclusively with the prick percutaneous testing.

Jennifer: Okay, and in terms of blood testing for allergies, which I have had clients, they've come back from their doctors with panels. What's your feelings on that? Is that worthwhile? Is there a time and a place for that?

Dr. Silvers: I think there's a time and a place for that. In general, we typically rely on the prick testing for those types of allergies first because in general, they're more sensitive than the blood test. When we compare prick testing and the lab testing, the sensitivity is about 75% with the blood test compared to the prick test. So if we can do the prick test, we prefer to go that route. But we can't always do the prick test. You have to be off certain medications in order to do the prick testing reliably.

Jennifer: Really?

Dr. Silvers: Like, antihistamine-

Jennifer: What type of meds?

Dr. Silvers: … Primarily.

Jennifer: Okay.

Dr. Silvers: Yeah. So you have to be off your daily allergy medicine. There's certain other medications we typically give patients that you have to come off of for so many days.

Jennifer: Okay.

Dr. Silvers: If you've got really bad eczema on the back or on your arms, maybe we can't do skin testing, things like that. So we certainly utilize the lab testing if necessary and it can be beneficial, particularly with food allergy. There are some new tests coming on that actually are showing very good sensitivity, particularly for peanut, which has come out. So things may be changing. But as of now, prick test is still the standard for which we judge everything else.

Jennifer: Okay. And let's say that I go have, so we're going to use food in this example, not dust mites, because I'm probably not ingesting dust mites. But let's say I get prick testing done and I find out that I have an allergy to walnuts and soy and eggs.

Dr. Silvers: All right.

Jennifer: But let's say I do regularly eat those things and I don't find that I go into anaphylaxis. So what do I do with that information? Or what questions should I ask my allergist about that? Because my concern, as a nutritionist, is I never want to encourage someone to eat something that could potentially trigger anaphylaxis, because that would not be good. But then clients oftentimes are confused because they might say, “Well, I've never actually reacted to these foods.” So how do you handle something like that?

Dr. Silvers: This is something we deal with regularly. Most of the time, I would tell that patient to throw the result in the garbage.

Jennifer: Really?

Dr. Silvers: The most important thing when diagnosing food allergy, in particular, is the history. What you tell me when you eat the food, what symptoms develop? Do you eat the food and there's no symptoms that develop? You don't have allergy. You shouldn't have been tested in the first place. Now this is specific for IgE mediated food allergy I'm talking about here. Those that are risk for anaphylaxis. One of the problem with allergy testing, whether it's skin prick testing, or lab testing, whatever it is, we get false positives. It happens. So you really have to interpret it with a keen eye to make sure that what you're seeing on the test corresponds to what the patient's telling you. And in many cases, those situations, it's a false positive. It doesn't mean anything. Patients can keep eating those foods without any problems.

Jennifer: In the instance where someone says they notice they start to get maybe itchy or they start to have maybe nasal congestion or their stomach gets upset, what would you say in that instance?

Dr. Silvers: Now that's different, right? Because you're eating the food and you are obviously having symptoms. And all of those symptoms you listed, they are consistent with an IgE mediated reaction. So that starts to make sense to me. That's when we have to start really thinking about avoiding the food strictly and we have to start thinking about keeping injectable epinephrine available, EpiPens and AUVI-Q devices. So that just makes a lot more sense when it corresponds with a positive test. So you kind of have to have both points.

Jennifer: Okay. So for anybody who's listening to this, it sounds, from what you're saying, you really do have to track some of this information, like either in a notebook and start paying attention to how you feel after consuming or being exposed to some of these foods. Because it could even be theoretically, like with flour, say you were allergic to wheat, flour can become airborne if say somebody opens a bag. So if, say you're in a room and someone wants to make Christmas cookies, they open a bag of flour, it goes up in the air and you start coughing and sneezing and wheezing. And you have a test that came back that said, you may be allergic to wheat. That would be an instance where you probably should have a conversation with your allergist about wheat in general?

Dr. Silvers: For sure. Absolutely. That's something to discuss. Now in that situation, getting something in your nose can cause you to sneeze, right? So it would certainly require some more evaluation. And in some cases we have to do food challenges and that is really the gold standard for food allergy diagnosis. This is a spot where if we're not sure exactly what's going on, maybe something isn't quite lining up perfectly with the history of the testing, we'll have someone come into the clinic and eat the food that we're concerned about. And we usually start with really small exposures and work our way up to bigger and bigger doses. That way we can introduce the food in a safe manner and figure out whether there is actually an allergy or not. Cause the important thing about that type of is, it's consistent. You eat the food, you should have symptoms consistently every time you eat it.

Jennifer: What about the type of person where we all know people that this has happened to, they ate shellfish for example, their entire life. And then the one time they had, I don't know, shrimp, lobster or something, they all of a sudden breakout in hives, maybe their mouth swells or they might start going into anaphylaxis. It happens.

Dr. Silvers: It does.

Jennifer: Cause I know people who that's happened to. Do you know why that kind of onset would happen?

Dr. Silvers: So I mean, that's kind of a million dollar question. And we're still learning about why food allergy develops in the first place. What we know now though, and this is probably more relevant to younger kids than to adults, but the sooner we can start introducing these allergenic foods and keep it in the diet consistently, that's the best way to help prevent food allergy from developing. So when I see some of these adults who develop seafood allergy, oftentimes they haven't had it in a year. It's not part of a typical American diet, depending on where you live. So they haven't had it for a while and because they aren't being exposed to it, they aren't maintaining their tolerance to the food. Next time they have it, bam, an allergic reaction because it's developed over time.

Jennifer: And so with kids, I don't work with children, but I have colleagues who do. And there's a lot of instances where, and I'm sure you see this, where maybe a baby or a young child starts to develop eczema. And then the mother, very well meaning moms, we understand, there's a lot of frustration, it's hard and you don't want to see your kids suffer. But sometimes they start going down this route where they start to cut food out because they've read online or whatever. They're like, “I'm going to take out gluten, I'm going to take out dairy. I'm going to take out this and that and corn and blah, blah, blah.” And the list gets longer and longer where the child, their diet becomes smaller and smaller. Is this, in your mind as an allergist, is that problematic potentially for a child in having so much pulled out of their diet like that?

Dr. Silvers: I try to avoid it at all costs, if I can. 20 to maybe 30% of kids with bad eczema, have a food trigger. The vast majority of kids do not have a food trigger for their eczema. Eczema, I think you have to think of as a skin problem first. It is a skin barrier issue where we lose moisture. The skin cells don't bind together very well. And that's where I focus almost all of the first visit when I'm talking to an infant with eczema. And then we have a lot of work to do typically before we get to the point where I start even thinking about taking foods out of the diet, because I think it's so important to keep these foods in the diet as best we can to help prevent the anaphylactic type of reaction to the food.

Now I've certainly seen kids where they do benefit from taking milk out of a diet. Eczema gets much better. It certainly happens, but it's really hard to pick out who those kids are. And you have to do it in a very precise manner in order to make it safe and to really know what you're dealing with.

Jennifer: And do you do this type of testing that we've discussed on children?

Dr. Silvers: We certainly can.

Jennifer: How do you do that? How do you do patch testing on a baby?

Dr. Silvers: Oh, okay. So patch testing is much less common for infants. The prick test is certainly something I do down to two months, if we need to. That's certainly something that's feasible and pretty easily done at that age, honestly. It's not overly painful and we may get a little cry at first, but many times they calm down really quickly and it's over and done with.

Jennifer: I wanted to ask you about the total IgE marker.

Dr. Silvers: Okay.

Jennifer: What is your thoughts on that marker? Is it something that you feel you should run if someone thinks they might have allergies? Is it helpful for you as an allergist?

Dr. Silvers: Only in very rare instances, is it very helpful for me. There are some very rare conditions where people can have really, really high levels of IgE. And that goes along with immune deficiency and things like this, which fortunately we don't see too many of those patients. But for your average patient with pollen allergies or food allergies, even eczema, it doesn't add a whole lot to what we do. One instance where it may help to a degree is, kids with eczema, and we're trying to evaluate food allergy. Kids with eczema, or even adults for that matter, tend to have very high levels of IgE. And when we get to levels as high as they can be, into the thousands, it can make interpreting some of the specific food allergy labs difficult. So it may change my approach to those patients. When we have a total IgE, that's much, much higher than is norm. But that's about the only situation. High IgE just tells me you're an allergic individual, your atopic.

Jennifer: And for someone who might come into your office, who says, “When I eat cantaloupe in the summertime, my mouth gets really funny. I feel like it's fuzzy or itchy. And there's some other foods that seem to do this too.”

Dr. Silvers: Yeah.

Jennifer: What does that tell you? What is that?

Dr. Silvers: Where am I? We're getting into all of that. I love it.

Jennifer: I know.

Dr. Silvers: Fruits and vegetables, typically when I hear this story, oftentimes are related to a condition called Pollen Food Allergy Syndrome, also called Oral Allergy Syndrome. This is a condition where there's proteins in the fruits and vegetables that are very similar in structure, like three dimensionally, to certain proteins in pollens. So when you eat these fresh fruits and vegetables, you get a mini pollen allergy reaction in your mouth. Most of the time, these symptoms are self limited, meaning they go away on their own. They tend to be relatively mild, lasting 10, 15, 20 minutes or so. And the important thing is, most of them don't progress to anaphylaxis. They don't go to a full body reaction usually because these proteins are very susceptible to heat and peptic digestion. So when they get to your stomach, those proteins get broken down very, very quickly. And your immune system doesn't recognize them as an allergen anymore.

That's why, in many cases, people with this Pollen Food Allergy Syndrome can eat the heated form of the food. Say an apple pie, whereas they can't eat a fresh apple, apple pie is perfectly fine, because it's been heated and those proteins have been broken down.

Jennifer: It's the funny thing when people are always like, “I just don't like apples, I just seem to react to apples. But I can have apple pie. It's like the craziest thing.” And I'm like, “No.”

Dr. Silvers: That's exactly what it is.

Jennifer: That's important.

Dr. Silvers: Some people can have it with bananas, that they can eat a ripe banana, but not a green banana, for example. So there's a lot of little nuance that people will find as they experiment with these foods.

Jennifer: So if somebody comes in and tells you this, do you then think, “Oh, we should probably check you for pollen allergies, as a result of that.”

Dr. Silvers: Yeah. Many times people will come in concerned about the food because they don't want to have anaphylaxis, obviously. But the real culprit is usually their pollen allergy. And in many cases, if we treat their pollen allergies, foods get better at the same time.

Jennifer: Okay. And out of curiosity, just in terms of “treating allergies,” I know you mentioned an EpiPen and obviously antihistamines tend to be one of the things that doctors can also utilize and do utilize. Do you feel like those are the best options or do you feel, in your opinion after doing all of this testing, that there are some newer options out there that people should potentially consider to help either manage or can they get rid of the allergies to some of these things?

Dr. Silvers: Well for food allergy, absolutely epinephrine is the drug of choice for bad reactions. There's no medication that's any better. It works quick and it's been proven time and time again to help prevent morbidity and mortality from food allergic reactions. So always that's the way to go first. Milder symptoms, oral antihistamines. Yeah, they work pretty well. But I never want someone to treat with an antihistamine when an epinephrine might be needed. We're talking more with nasal allergies for example, nasal sprays, things like Flonase, Nasonex, Nasacort, those tend to be some of the better allergy medicines. Trouble with those is they need to be used on a fairly consistent basis. They don't work very quickly like oral antihistamines can. So those are the two classes that are the most commonly used. And we have a few other things we can try, but usually not as good as those.

Jennifer: Do you ever utilize some of the more massed stabilizing drugs, like Ketotifen, that at times, I've had some clients that have been on them because they're reactions are just seem to be so severe.

Dr. Silvers: On occasion. Yeah, absolutely. So there are a group of patients that I see, let's say with Mast Cell Activation Syndrome, and that's a topic for another time, but they do benefit from things like the mass cell stabilizers, absolutely. Another group would be Leukotriene modifiers like Singulair is the most common one, montelukast. So there are other ones out there that we can utilize now.

Jennifer: Cool. Oh my goodness. I was like, “Is he going to know about?” I wasn't sure I was throwing you a curve ball there. The mast cell, I just, it came to my mind, I thought I'd ask. I must say, this is helpful because being a clinical nutritionist, allergies weren't something that we were heavily trained in. And obviously unless you have… I didn't train in an allergist's office. My dad was an ophthalmologist, there was plenty of things I saw in his practice that I'm sure do not exist in other areas. Like a cardiologist has different ways of doing things and unless you're really in it, you don't understand the difference.

And this is what I was saying. You're telling me about these different types of testing and I'm like, “Wait, so does is it mean this?” And that's literally how this whole conversation can go sometimes. And clients aren't sure what to ask. They're not sure what to even ask for, and they're not sure what the results even mean. And sometimes the results aren't well explained. And so this is really helpful for people to know the difference between them. And you work as part of a practice. Your practice is in many different states, is that correct?

Dr. Silvers: Yeah, that's right. Aspire Allergy & Sinus. We are in five states currently, with multiple locations in each one. So we are around to help demystify allergy as much as possible. Food allergy in particular is one of my passions and I do do treatment for food allergy, if necessary. It's something that's near and dear to my heart. So if you have anyone out there in the Austin area, let me know.

Jennifer: Very, very cool. Well thank you so much for being here and for everybody who is listening to this, if you are looking for an allergist to help you on your journey, you can go check them out at aspireallergy.com and you will all hear, not only Dr. Silver, but also Dr. Thompson is joining us as well on the show. And it's so great to finally have some space held and carved out for people who have questions around allergies or who are struggling with allergies and just would like clarity. Because as you and I both said, it's kind of confusing.

Dr. Silvers: It can be, absolutely.

Jennifer: For those of us on the patient side. But thank you so much for joining us today. I appreciate it.

Dr. Silvers: Oh, thanks so much for having me. Appreciate it.

“That's one of the benefits of (skin prick) testing is you get quick results, usually before you even walk out the door. So that test is very good for nasal allergies, food allergies, anaphylactic type reactions."