October 30, 2017

Expert Q&A: Food allergies


Food allergies can develop at any age. Learn more about the signs.

Food allergies continue to be an important topic as more are diagnosed. They can develop for anyone, at any point, at any age. Here, Alice Hoyt, M.D., of the Vanderbilt Asthma, Sinus and Allergy Program answers questions about the nature of food allergies and how they are detected and treated.

Question: Are food allergies increasing or are we just hearing about them more in the media?
Answer: It’s kind of both. Food allergies are certainly being diagnosed more. We have more testing, but millions of people suffer from food allergies, both adults and children.

Question: Can you develop food allergies that you didn’t have as a child?
Answer: You certainly can. We see that a lot of times with shellfish like shrimp, crab. We also see it though, with the mammalian meat allergy called alpha-gal allergy, in which a person is bitten by a tick then a couple months later begins having hives, swelling, anaphylaxis to mammalian meat products.

Question: What are the most common food allergies?
Answer: The big ones are peanuts, tree nuts, eggs, milk, wheat, soy, fish and shellfish, and then we have some other less-common kinds. But really the most important thing is to see an allergist to discuss if you think you have a food allergy of any kind.

Question: How long does it take for an allergic reaction to occur?
Answer: That’s a very important question. If you’re concerned that you’re having an anaphylactic type of reaction, with most food allergies – peanuts, tree nuts, eggs, wheat, soy, fish, shellfish, those types of food allergies – you generally know pretty soon after you eat it. You’ll start having hives, swelling and trouble breathing, and your blood pressure can drop so you have this sense of what we sometimes call “impending doom.” It can be very scary, but there is a medication to treat it: epinephrine. Epinephrine is the only medication that will actually stop the allergic reaction. Again, generally these reactions occur pretty immediately, unless you have that mammalian meat allergy, alpha-gal allergy; then we actually see a delayed response. You could eat the meat and then two, six, sometimes eight hours later, that’s when you have the reaction.

Question: What if you just have a really mild reaction, like you just get hives? Would it be important to see an allergist, or do you just stop eating that food and go on with your life?
Answer: The first thing to do if you think you’re having a reaction to a food is to avoid it until you talk with a specialist: an allergist. Then we can do testing to help determine, in conjunction with history, what type of reaction that was, so you can understand the immunologic process going on in your body. We can prognose where you’ll be with this allergy. With mammalian meat allergy, sometimes that can resolve, especially if you avoid tick bites. But, for example, with a peanut allergy, if you develop it when you’re a young child, you only have about a 20 percent chance of outgrowing it. With cow’s milk allergy, it’s an 80 percent chance. It’s really important to discuss those things with an allergist and really, the term severe life-threatening allergy, can be applied to anybody who has a food allergy, because having hives one time does not mean that next time it will only be hives. That’s why it’s so important to talk with your allergist about this.

Question: Can you talk a little bit more about growing out of allergies and how often that happens?
Answer: I had a 17-year-old patient who we’ve been following; we tested him, and we were able to reintroduce peanuts safely. Those success stories are happening every day! There’s certainly hope that that will happen, but again it’s important to be in contact with your allergist. See him or her regularly, at least annually, to discuss these things. But generally, for peanuts, there’s a 20 percent chance of outgrowing it if you’re diagnosed when you’re young; for cow’s milk, egg, other allergies, about an 80 percent chance. We don’t really understand why some allergens are more allergenic per se, than others foods, but they are. And I think as science continues to progress and we continue to explore these issues, then we’ll get more answers.

Question: Can you just talk a little bit about how it’s confirmed that a person has an allergy? What’s that process like someone sees an allergist?
Answer: I would say 90 percent of it is really the history. Talking with the specialist about what your symptoms were, what you ate, how long after eating, what exactly happened, how that reaction was treated, that’s going to tell us 90 percent of the time whether this was anaphylaxis. Then what we’ll do is skin testing and/or blood testing to help us better clarify the clinical picture. Then if the skin testing and blood testing’s negative, if the history was less consistent with the classic anaphylactic type reaction, then we might consider an in-clinic food challenge, where we’ll have you bring in the food, and eat it right there with us, and move forward with your life so that you’re not necessarily avoiding a food that you don’t need to avoid. That being said, we don’t proceed with those food challenges lightly. We’re only going to do it we think it’s safe.

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Contact Vanderbilt Asthma, Sinus and Allergy Program for an evaluation and the most up-to-date treatment recommendations. Call 615-936-2727 for an appointment.