The Most Common Food Allergies to Develop as an Adult

Most people think of food allergies as a childhood problem, but more adults are developing them than ever before. Here's what you need to know about adult-onset food allergies.

Most people think of food allergies as a childhood problem. That’s a fair assumption: It’s very likely that food allergies will develop early in life, says Sarita Patil, MD, allergist at Massachusetts General Hospital Food Allergy Center and instructor at Harvard Medical School. Some food allergies can be outgrown—milk and egg allergies are among the more common—while others, like peanut and shellfish allergies, are more likely to persist into adulthood.

But any food allergy can technically develop at any time, Dr. Patil says. “Adult-onset food allergies are obviously more rare, but they do happen,” she says. “They can happen at any age—I see food allergies develop in advanced age as well.”

In fact, a 2019 study of over 40,000 U.S. adults, published in the journal JAMA Network Open, found that there are at least 12 million U.S. adults with adult-onset food allergy. That’s more than previously believed. Research published in 2017 in the Internal Medicine Journal also suggests that the prevalence of food allergies in all ages has increased significantly in the past two decades, and continues to rise.

So, we spoke with board-certified allergists to find out how to assess your risk, which food allergies are most common in adults, and what to do if you suspect you’ve developed a new-to-you food allergy.

Causes of food allergies

A food allergy happens when the immune system overreacts to a certain food, says Purvi Parikh, MD, allergist and immunologist with Allergy & Asthma Network and clinical assistant professor at NYU Grossman School of Medicine. For some reason, the immune system becomes hypersensitive and develops antibodies to “fight” against the food, as if it were a dangerous intruder like a virus or bacteria. What we recognize as allergies—swelling, itching, redness, and more—are the result of this immune reaction.

“It’s hard to know why allergies develop in some people and not others,” Dr. Parikh says. Experts have some theories. One is the hygiene hypothesis, which suggests that modern obsession with avoiding germs prevents our immune systems from building the tolerance it needs, resulting in glitches like allergies. Along those same lines, certain chemicals like disinfectants and pesticides have been linked to allergies, which experts suggest could have something to do with how they kill both bad and good bacteria.

Other risk factors

Genetics seem to play a significant role in allergy development, too. “Having one parent with any type of allergy increases your risk of having a food allergy by 50 percent,” says Dr. Parikh. “They don’t have to have food allergy, it could be another type and that increases your risk.” Experts tend to think allergies develop as a perfect storm of both genetics and environmental factors.

Allergies also tend to hang together, says Dr. Patil, meaning that people with any allergies tend to have multiple types.

Early exposure to certain potential allergens, like peanuts, can help prevent young children from developing food allergies, according to the National Institute of Allergy and Infectious Diseases. But doctors haven’t been able to pinpoint any sort of preventive measures to stop food allergies from happening later in life.

Food allergy vs. intolerance and sensitivity

Food intolerances and sensitivities are real, but the difference is that these food reactions are not sparked by an immune response, Dr. Parikh explains. The causes of an intolerance or sensitivity vary, but usually are related to how the body breaks down or digests a certain food, like lactose intolerance or gluten intolerance.

While intolerances and sensitivities can definitely make you feel uncomfortable, they’re not dangerous or life-threatening, Dr. Parikh notes. Many people might experience intolerances and sensitivities to varying degrees, sometimes resulting in severe discomfort, but they can’t cause a catastrophic reaction like an allergy can.

Types of food allergies—and their symptoms

IgE-mediated food allergies

The most common food allergies are caused by that immune system overreaction and production of antibodies to fight a particular protein in a food. These are referred to as IgE-mediated food allergies—IgE stands for Immunoglobulin E, the scientific name for those antibodies. These are the kinds of food allergies that can cause anaphylaxis, a life-threatening whole-body reaction that can impair your breathing, cause a dramatic drop in your blood pressure, and affect your heart rate.

Symptoms

They usually occur almost immediately after ingesting the food and include swelling of the lips and tongue, hives, itching, redness of the skin, vomiting, and in severe cases, breathing problems, loss of consciousness.

Hypersensitivity

Another type of food allergy is called non-IgE-mediated food allergy (or hypersensitivity). These are caused by a different immune response that doesn’t involve IgE antibodies, though experts aren’t totally sure exactly what triggers them.

Symptoms

These allergies are usually delayed, and cause symptoms in the gastrointestinal tract, like vomiting, bloating, and diarrhea. They don’t cause anaphylaxis.

Eosinophilic esophagitis

This is a relatively rare but increasingly recognized allergic disease, Dr. Patil says. It happens when food or an environmental allergen prompts eosinophils, a specialized cell in the immune system, to accumulate in the esophagus.

Symptoms

It can cause inflammation that leads to difficulty swallowing, food getting stuck, heartburn, and chests pain. “In adults, it can manifest as choking,” says Dr. Patil.

Oral allergy syndrome

Another immunological response to food is something called oral allergy syndrome. It’s also called pollen-food syndrome, Dr. Patil says, and is probably more common than we know. When the body is sensitive to a specific protein in pollen, it can lead to a cross-reaction in fresh fruits, vegetables, and nuts that contain the same protein. “Oftentimes, people will have seasonal allergies and out of the blue will develop oral allergy syndrome,” Dr. Patil says.

Symptoms

This allergy most commonly causes itching in the throat, mouth, and tongue. Despite being uncomfortable and similar to an IgE-mediated food allergy, oral allergy syndrome typically doesn’t cause anaphylaxis (though in a very small number of people it can), Dr. Patil notes. 

The most common adult-onset food allergies

Although it’s possible to develop any food allergy at any age, the most common adult-onset food allergies are fruit and vegetable pollen (oral allergy syndrome), fish and shellfish, and peanuts and tree nuts, according to the American College of Allergy, Asthma & Immunology.

All of these allergies may also result in cross-reactions with foods that have similar triggering proteins. For example, there’s a link between dust mite and cockroach allergies and shellfish allergies, thanks to a similar protein found in all of these things. So, if you’re allergic to dust mites, which Dr. Parikh says is very common, you have more chance of becoming allergic to shellfish. If you’re allergic to one type of tree nut, you may become cross-reactive to others.

Pre-existing allergies can make it more likely for someone to develop a new allergy, but there isn’t a clear reason why these allergies are more likely to develop in adulthood than, say, an egg or milk allergy.

Diagnosing food allergies

“If you experience breathing problems or vomiting associated with rashes, seek medical attention right away,” Dr. Parikh says. That means going to the ER or an urgent care clinic. If you experience only a food allergy rash, you should still consult a physician and ask about being tested by an allergist, she adds. Food allergy testing can be done in a few different ways. Your allergist may do an oral challenge test, where he or she gives you a small amount of the suspected food and monitor the reaction; they may do a skin prick test, which basically places a small amount of the suspected food into a scratch on your arm or back to see if it causes a reaction; and they’ll likely do a blood test to look for IgE antibodies to confirm any suspected allergy. Allergy tests can also determine whether you have a true allergy, an intolerance, or a sensitivity.

Getting tested and properly diagnosed is important, even if you just had some itching and redness. Just because you had a minor reaction the first time doesn’t mean that will always be the case, Dr. Parikh says. And although allergy tests can tell whether you’re highly reactive to an allergen, it’s still hard for doctors to predict how you’d react every time you’re exposed.

Living with a food allergy

Since the severity of your reaction can vary with each exposure, Dr. Parikh says it’s best to just completely avoid a food that you’re allergic to. That can be hard if you’re eating at someone else’s house or at a restaurant.

“The safest food is the food you prepare yourself,” Dr. Parikh says. Otherwise, you need to be very diligent about reading labels on the foods you buy, and always tell your server or the chef what you’re allergic to. It’s also a good idea to call ahead to make sure a restaurant or eatery can accommodate your allergy, and make sure your friends and family are aware of your allergy. It’s OK to be aggressive about it, Dr. Parikh says. A food allergy can be life-threatening, after all.

If you do eat meals outside of your home, always carry your epinephrine autoinjector just in case. Again, you can’t fully control what you eat unless you prepare it yourself, so you need to have a safety plan in place just in case there’s a slip.