October 30, 2017

Expert Q&A: What to know about food allergies

by

People can outgrow food allergies. Learn how to know if you’ve left yours behind.

Food allergies continue to be an important topic as more are diagnosed. Food allergies can develop at any age, but most cases begin during childhood. 

At the Vanderbilt Asthma, Sinus and Allergy Program, Basil Kahwash, M.D., answers questions about food allergies and how they are detected and treated.

Developing food allergies

Question: Are food allergies increasing or are we just hearing about them more in the media?
Answer: Both. We certainly have better testing now and that has improved our ability to diagnose. But there’s no question that the number of people with a food allergy is increasing, both among adults and children.

Question: Can you develop food allergies that you didn’t have as a child?
Answer: Rarely, but it can happen. We sometimes see that with allergies to shellfish (shrimp, crab, oysters, etc.). There’s also a recently described condition called alpha-gal allergy, which is a potentially serious allergy to meat from mammals that develops after a person experiences a tick bite.

Question: What are the most common food allergies?
Answer: The “Big 9” are peanuts, tree nuts, eggs, milk, wheat, soy, sesame, fish and shellfish. These are the foods that are required to be highlighted on ingredient labels as a warning to people with allergies. But if you think you have a food allergy of any kind, whether it’s a common allergen or not, it’s best to get checked out by an allergist.

Food allergy symptoms

Question: How long does it take for an allergic reaction to occur?
Answer: That’s a very important question. A life-threatening, anaphylactic reaction starts very soon after eating, usually within minutes. Patients will often have other food allergy symptoms like hives, swelling and trouble breathing, and in very severe cases their blood pressure can drop and they develop a sense of “impending doom.” It can be very scary, which is why we recommend patients carry injectable epinephrine (for example, an EpiPen) to use in these emergencies. Epinephrine is the only medication that works by stopping the allergic reaction in its tracks.

An exception to the “immediate reaction” rule is the alpha-gal allergy, that allergy to meat that comes from mammals that I mentioned before. In alpha-gal syndrome there is a delayed response. You could eat meat and not have a reaction until two, six, or even eight hours later, and then develop serious food allergy symptoms.

What to do if you suspect an allergy

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: if it’s hives, you want an allergist. However, hives can have other causes and I’ve seen patients eliminate foods when they really didn’t need to. Usually, the combination of asking questions and testing allows allergists or immunologists to determine the diagnosis — whether it’s a true allergy caused by the immune system’s rejection of the food, or just an intolerance to the food, or something entirely unrelated to food. If you do happen to be allergic, we can give you a prognosis. 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, and even higher for certain types of patients.

Testing for food allergies

Question: Can you just talk a little bit about how it’s confirmed that a person has an allergy? What’s the food allergy testing process like when someone sees an allergist?
Answer: The biggest clue is the patient’s history. Our goal in the beginning is to use the story to determine whether a reaction might have been anaphylactic. After that, we often do skin testing and/or blood testing to the foods in question to help clarify. Then if the diagnosis is still in question, we might consider an in-clinic food challenge. For this, a patient brings in the food and eats it under a doctor’s observation. If you can eat the food without reacting, congratulations – you’re not allergic! I should be clear that we don’t proceed with these food challenges lightly. We’re only going to do it if we think it’s safe, and we keep treatment on hand in case a reaction occurs.

Growing out of an allergy

Question: Can you talk a little bit more about growing out of allergies and how often that happens?
Answer: There’s a lot of data now showing not only which food allergies are likely to be outgrown, but how to use allergy test results to determine how likely it is that a patient is no longer allergic. I do food challenges in my clinic every week, mostly for patients who have been told they’re allergic to a certain food since childhood. Most of my patients pass their challenge. I’ve seen patients and relatives shed tears of joy when they find out they no longer have to go to such lengths to avoid a food.

If you have a food allergy you really should be seeing an allergist who can help you decide when you might be a candidate for a food challenge. See him or her regularly, at least once a year, to discuss your latest progress and consider getting re-tested. There might be things you can do to increase your chance of outgrowing an allergy. For instance, patients who have egg allergy but can eat baked eggs (like in cake) improve their odds of outgrowing the allergy if they keep the baked egg products in their diet.

I should also mention oral immunotherapy (OIT) here. This is a promising medical advance that has allowed some patients with food allergy to become “de-sensitized”. It’s not a cure, but it does reduce their risk of a life-threatening reaction if they take the medicine every day. So far only peanut OIT is FDA-approved but I expect more foods to join the OIT party soon.

Read more

How to manage food allergies at school

Learn more

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.