Dr Brian Lacy dispels some myths and clarifies the issues surrounding food allergies and food sensitivities and provides guidance in how to treat both conditions.

Brian Lacy, MD, is a professor of medicine at the Mayo Clinic in Jacksonville, Florida.

TRANSCRIPT:

Welcome. I'm Brian Lacy, professor of medicine at Mayo Clinic in Jacksonville, speaking from Vancouver, British Columbia at the annual ACG American College of Gastroenterology meeting. And for the next few minutes, I'd like to discuss a lecture that was presented at ACG on food allergies and food sensitivities. As a practicing clinician, I see patients all the time who come in and they're really worried about whether or not their symptoms represent a food allergy or food sensitivity. One of the difficulties as a clinician is that many of the symptoms reported —fullness, pressure, discomfort, bloating, nausea—are very nonspecific. So our job as a clinician is to really think about how do we identify a patient with a true food allergy? How do we explain it to that patient and how do we distinguish patient with food sensitivities?

So kind of what's my algorithm that I've kind of worked on over the years? So let's think about a food allergy first, and I'll mention a few myths and misconceptions. A myth is that it's actually very uncommon, and that's not true. Food allergies in adults are actually more common than we think, about 2% to 7% of adults. The next myth is that if you just read a label, you'll understand what's in the food and therefore you won't have an allergic reaction. Not true at all. All of us probably heard about that terrible death just about 10 days ago of a world-famous chef who died of a food allergy. So we're not always just by reading labels can we identify that.

What are some of the most common food allergies? As we know, they are cow's milk in adults. They are peanuts, they are shellfish, they are strawberries. They can be honey and other tree nuts as well. And so those are the most common ones. What are the most common symptoms of a food allergy? Most of the time these are IgE-mediated events, so immunoglobulin E. And remember, to make the accurate diagnosis of a food allergy, you want to hear the classic symptoms— periorbital fullness, swelling, numbness, tongue swelling, rhinorrhea, the signs of angioedema, shortness of breath— the classic symptoms. And it has to be reproducible. Not just it occurs once in a while, very randomly. But if you take that food that you're allergic to, you have a reproducible event.

So how do you make that diagnosis? One, you get a great history. Number two, you have the classic symptoms. And then number three, make sure you send that patient to see an allergist and they can do a skin prick test. Now, when you think about skin prick tests, these are good tests but not great tests. So they are support of the diagnosis. The diagnosis of a food allergy, again, about 2% to 7% in adults, is based on the classic history of reproducible event. It's this immunologic event. And then with a skin prick test, you can measure IgE responses and the size of the wheel may help determine it.

In a patient with a vague history and a negative skin test, a skin prick test, the negative predictive value is more than 90% and you can confidently tell that patient that they don't have a food allergy. Treatment of course,,you avoid the foods, you're working with the allergist and you have an EpiPen. That said, when we think about food allergies, I mentioned 2% to 7% of adults; most patients have food sensitivities, and these are not immune events. They're basically an intolerance to food. They can occur due to enzyme defects. Think about lactose intolerance. You're missing lactase. They can be a pharmacologic event. Think about salicylates. And salicylates can be found in different foods such as apples. They can be due to even an anatomic issue.

So when you think about food sensitivities, which are really the vast majority of food related complaints, remember too, it's a big umbrella term, you have to really put on your thinking cap and go through this long laundry list. So thinking about your patient who comes in with food related complaints, the first thing you need to do is make sure it's not a food allergy. Take the complaint seriously. You would not want to miss that because of the possible anaphylactic reactions. Again, coming from Vancouver, British Columbia, I hope you enjoy the ACG meeting and look online and we'll get you all the resources you need.