Resources

  1. Gupta RS et al. Prevalence and Severity of Food Allergies Among US Adults. AMA Netw Open. 2019;2(1):e185630


Transcript

Dr. Frank Domino:

Alex is a 42-year-old office manager who comes in for a follow-up of a recent emergency room visit. He had a dinner at an Italian restaurant that included pasta with clam sauce. He started to have difficulty breathing and an ambulance took him to the hospital. There he was given an epinephrine and prednisone and told to follow up with his primary care provider.

Hi, this is Frank Domino, family physician and Professor in the Department of Family Medicine and Community Health at the University of Massachusetts Medical School. Joining me today is Dr. Alan Ehrlich, Associate Professor in the Department of Family Medicine and Community Health, and Executive Editor of DynaMed. Alan, thank you very much for coming in today.

Alan Ehrlich:

Thanks Frank. Nice to be here.

Dr. Domino:

Wow, so Alex went out for one of my favorite meals that ended up in the emergency room. What's going on here?

Alan Ehrlich:

Well, of course, it's always difficult to tell from when a patient comes in and says, "I think I ate something and I had a bad reaction. What exactly caused it?" But on the basis of what we've heard, this is likely a shellfish allergy and shellfish allergy is the most common food allergy in adults.

Dr. Domino:

Wow, no kidding, shellfish allergy. Or are these kids who had selfish allergies or some food allergy growing up, and then just persisted into adulthood, or is this something new?

Alan Ehrlich:

So, there was a recent article in the JAMA Open Network that looked at the prevalence and severity of food allergies in adults, and one of the things that it looked at was how frequently adults develop new onset of food allergies. About 25% of adults with food allergies only have them as an adult. Another group developed them as children, but may either continue to have that same allergy or there are some who develop a new food allergy. Many people are allergic to more than one food who have food allergies.

Dr. Domino:

Really? So it sounds like you can... One in four people with a food allergy as an adult develop it in adulthood. Is that right?

Alan Ehrlich:

That's exactly right.

Dr. Domino:

Can you tell me a little bit about how we know whether this is a food allergy? I mean, obviously Alex started having respiratory symptoms. That's quite severe. What are some of the symptoms that make you certain this is a food allergy rather than just maybe an emotional or a slight intolerance?

Alan Ehrlich:

First of all, it can be hard to tell at times, and the most important thing is to take a clear history. One of the things they found in this study was they asked the people in this survey, and it was a large survey of 50,000 respondents approximately, and about 20% said they had a food allergy. Of those, on clear history taking, probably only about 10% had what they described as a convincing food allergy. Of those 10%, only half had been diagnosed by a physician. But again, the researchers felt that there was at least 5% of this population that had convincing food allergies, even if they weren't diagnosed by a physician. So, many people who will just say, "Listen, I get this allergic reaction." They don't go to a doctor, they may still have a food allergy. But in terms of, what are the symptoms, it can range from things that you would expect, such as hives, any type of skin reaction. You may have some oral mucosal things, such as lip swelling or tightness in the throat. You can have full-blown anaphylaxis. And sometimes you'll have other symptoms, GI symptoms. Belly pain, diarrhea chest pain, tachycardia, things like that. It's really quite a range of symptoms that can be the manifestations of food allergies.

Dr. Domino:

Let's think about it a bit. You have a patient who comes in who thinks they are having some food allergy. How do we discern if it's just an intolerance? Do we do any kind of special testing? Does everyone get referred to a gastroenterologist or an allergist?

Alan Ehrlich:

So again, the first thing is, a detailed history. What is the time course? How likely is it that the symptoms might have been caused by something else? What other conditions might mimic this? So for instance, there's a difference between a milk allergy and just being lactose intolerant. And that can often be hard to tell, but that's something that should be determined. And certainly, there are different tests for lactose intolerance than there are for milk allergies. The same thing with wheat allergies. A wheat allergy is not the same thing as celiac disease. Celiac disease is IgA mediated. A wheat allergy should be IgE mediated, and the celiac disease is to the gluten component, it's not to the wheat itself. So trying to tease those things apart is one of the first steps. If you're not sure, based on the time course of, "I've eaten this food and gotten this reaction." The next set of testing to do would be either IgE serum samples, specific for the food in question, or skin testing, but you should only do it when there's already a reasonably clear convincing story that you're trying to confirm, because there'll be a lot of false positives if you're just using it as a screening test.

Dr. Domino:

Alright, that makes good sense. When should you be doing testing for celiac disease, for example? If someone comes in and says, "Oh, I ate something and I get explosive diarrhea and I break out in a rash." What would tip you in the direction? And what would you order if you were thinking that the patient might have celiac?

Alan Ehrlich:

The rash that's most common with celiac disease is dermatitis herpetiformis, and that really is different than hives or atopic dermatitis that some people will get, although certainly people with celiac disease can have both. But there's a much tighter time course, and again, most food allergies are going to be to other substances, but if you thought someone had celiac disease, you could get serum levels for anti tTG antibodies. And ultimately though, to diagnose that, you're going to need to have biopsies of the small intestines, in most cases. There's recently some guidelines on celiac disease that in very narrow circumstances you can probably do a valid diagnosis without an intestinal biopsy, but for the most part, they're gonna need a GI referral.

Dr. Domino:

Alright. So Alex comes in, he's eaten a meal he obviously wanted to eat. Is it okay for him to try eating pasta with clam sauce again? Is he going to have to avoid all shellfish for the rest of his life? How should we be counseling our adult patients who we believe have a food allergy?

Alan Ehrlich:

So, first of all, if you think they have a true food allergy, and again, let's talk about the most common food allergies in adults, which will be shellfish, peanuts, milk, tree nuts and fin fish. If you are having any type of clear allergic reaction, those people probably should have epipens, because the reaction, the first time is not necessarily a predictor of what the reaction will be the subsequent time. It can certainly be more severe. I know many the people I work with, it seems like there's more and more food allergies around us, and I do know some people with tree nut allergies, and they're extremely sensitive and they wind up in the emergency room a lot.

I was on a plane recently, where there was an overhead announcement saying, "Please do not eat any food you have brought yourself that has tree nuts, because there's someone who's allergic on the plane and the air recirculates." And whatnot. So this stuff is out there and these people can be exposed inadvertently, even if they're being very diligent. So, epipens should be prescribed for those people. Certainly anyone who's had a severe reaction, anything that involved than one organ system, where perhaps they're having a rash, and they're having some hypotension or tachycardia or things like that. These people need to be evaluated by an allergist and assessed for what additional treatments besides an epipen might be warranted.

Dr. Domino:

Wow. Well Alan, thank you very much. I feel badly for Alex, but I think it's better to be safe than sorry, and having him skip the clam sauce in his future seems like a good idea. It very much helps to know what the workup should be, and that we should be counseling people and offering them an epipen. Thanks again.

Alan Ehrlich:

Thanks Frank.

Dr. Domino:

Practice pointer. Food allergies in adults are on the rise. If a patient's tried eliminating that food from their diet, and are continuing to have symptoms, consider referring them for allergy evaluation. Join us next time when we talk about sexting and it's rising prevalence among the US teenagers.