Common food allergies

Stuck in the middle of the food allergy era

More kids and adults are finding out they can't eat this or that. We ask an allergist why.

If and when my youngest daughter starts a heavy metal band, she already has the name: Death Nutz.

She came up with this one day when, shortly after being diagnosed with a tree nut allergy, I mistakenly offered her a snack with walnuts. "Thanks, Dad … for trying to kill me," she deadpanned.

Food allergy is a potentially life-threatening medical condition that affects 32 million Americans, including 5.6 million under the age of 18. Every three minutes, a reaction sends someone to the emergency room, according to the nonprofit Food Allergy Research & Education.

Panida Sriaroon

Image caption: Panida Sriaroon

Image credit: Illustration by Montse Bernal

In the U.S., the eight most common food allergens are milk, egg, peanut, tree nuts, soy, wheat, fish, and shellfish. And the problem is getting worse, with an ever-growing number of people becoming allergic to more and more types of foods. Sesame is the new kid on the block, and, while rare, some legumes and spices can cause reactions, too.

Food allergies—a result of an overreactive immune system—can vary unpredictably, from mild to severe. One person might experience a few hives or minor abdominal pain, while others might quickly progress to severe¬†anaphylaxis and loss of consciousness. Currently, there is no cure for food allergies. But we do have treatments.

Panida Sriaroon, an allergist and immunologist at the Johns Hopkins All Children's Hospital, has been on the forefront of treating food allergies with oral immunotherapy to desensitize patients with a severe food allergy. Johns Hopkins Magazine spoke to Sriaroon about how we got here and how we can stem this allergy torrent.

Why are we seeing more cases of food allergies now than in perhaps all of human history?

The honest answer is we don't really know. It could be simply because we're more aware of it. However, we cannot deny the fact that there are a lot more people right now with true food allergies than ever recorded. It's not just food intolerance—like my body doesn't agree with a certain food when I eat it—we're talking about serious, life-threatening allergies. And we see a lot more of those now, especially in the developed countries.

Can you define food allergy and the spectrum of associated symptoms?

There are several types of reactions, ranging from mild, to moderate, to severe, to life-threatening. Around 70% to 80% of the time, a reaction will start with a rash around the face and mouth. Then the person might get itchy eyes, itchy nose, sneezing, or a swelling of eyelids or lips. They might get hives elsewhere on the body. In the worst cases, a person will experience anaphylaxis, the term for a severe allergic reaction, which could mean diffuse hives all over the body or a throat closing. So, basically, it's a constellation of serious symptoms.

What is happening in the body when you eat a food you're allergic to?

It's similar to any kind of allergy, such as cat hair or dust mites, where your immune system reacts abnormally to a foreign substance. In the case of food, however, the route of exposure is different. For environmental allergies, we're talking about eye exposure or inhalation. For food allergy, we're talking about ingestion. However, highly sensitive individuals might develop a reaction even just with contact exposure. For example, people with a serious peanut reaction might get hives all over after just slight peanut butter contact to their lips. Some people have told me, "I can't go on an airplane because someone five rows ahead of me might open up a bag of peanuts." A person who is allergic to fish could start coughing simply after inhaling the fumes of the fish odor from cooking.

Humans should be able to eat a fish or a nut and not have a severe reaction, or else, well, we wouldn't still be here. Why is this happening?

You are correct that humans wouldn't have survived this long if these allergies always existed. However, the foods we eat these days are different from those we ate a decade ago, let alone a million years ago. Just think about how foods are eaten, and more specifically how they're processed. We eat frozen fruits, canned foods, foods that are precooked, pre-washed, and kept fresh with all kinds of preservatives and additives. It's hard to say whether these foods are digested and recognized by our bodies in the same way as what our ancestors ate.

I'm fascinated by this idea that playing in the dirt is good for us and that we're way too clean for our own good.

Right now, we're gung-ho about everything being spotless and clean. We sanitize. We use hand wipes. We use disinfectant spray all the time. Even our pets are so clean. We're not exposed to a lot of germs anymore. Germs are good things. We recommend outdoor play and vitamin D exposure via sunlight. So go ahead: Run outside and swim in a pond.

We also don't expose ourselves to foods early enough. For example, in Asian countries they eat a lot of nuts and peanuts as condiments. I always hear from patients coming from other countries who are like, "What? There are a lot of peanut allergies in this country. We have none." Is it because they start exposing babies to peanuts early? Maybe.

We simply grow out of some food allergies, correct?

Usually, it gets better with age. If your young niece or nephew has milk or egg allergies, there is a decent chance that they will grow out of it completely. But if it's, let's say, a cashew allergy, chances are they will go on to have a lifelong cashew allergy.

Tell me about your treatments. The oral immunotherapy you're using is basically microdosing the very food you're allergic to, correct?

We call it tolerance induction, desensitization, or immunotherapy. This is a similar concept to allergy shots for oak allergy or bee sting allergies. This intervention is designed for people who are highly allergic, where even a small amount of the food can cause severe reactions. But they can't live in bubble, so we want to gradually bring up the threshold of what the person can tolerate. Maybe at the start they can't eat even 1/100th of peanut protein without having a serious reaction. In the case of peanut allergy, we introduce minute doses of peanut protein (0.5-mg to 300-mg) via a drug called Palforzia, so in six months they can tolerate up to the equivalent of one peanut a day. But this is not a cure. You're going to need to take the treatment every single day indefinitely to maintain tolerance.

The goal is to be safe in case you accidentally eat the food you're allergic to. But if they achieve the tolerance of one peanut a day, and they turn 18 and go to college, and they're like, "This is not for me; I hate it," they stop taking oral treatment. Within a few weeks, their body will revert to the pre-treatment stage.

What do you recommend parents do to perhaps limit the number of food allergies a child has?

We know that there are ways to prevent development of food allergy to a certain degree, and that is to introduce highly allergenic foods early on. Instead of waiting until the child turns 1 year old to introduce peanut butter, let's do it sooner, maybe at 4 to 6 months old. We want the baby to eat the food by mouth. We recommend starting with thinned out peanut butter, maybe mixed with breast milk or formula.

Peanut is just one obvious example, but the same is likely true for eggs, tree nuts, or other foods. The earlier, the better. Don't wait.

Greg Rienzi is the editor of Johns Hopkins Magazine.

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