Why Do We Develop Food Allergies as Adults?

Fact checked by Nick Blackmer

• Since the immune system is constantly evolving, it's always possible to develop a new allergy to familiar things.

• People who have eczema might be more prone to food allergies because allergens could enter through breaks in the skin.

• If you suspect you may have a new allergy, keeping a food diary can help identify possible triggers. You can also get a skin prick test or blood test to confirm a diagnosis.
  

You can develop a new allergy at any age, even if you’ve never had allergies as a child. In fact, recent research shows that more people are developing food allergies in their adulthood.

A 2019 study estimated that of the 26 million U.S. adults with allergies, at least 12 million—or 48%—had developed an allergy as an adult.

“Allergies are the result of an error in our immune system, one in which we misidentify a harmless thing as being harmful and then try to get rid of it by creating inflammation,” said Brian Greenberg, MD, an allergist, immunologist, and a formulator for 1MD Nutrition.

Why Do Adults Develop New Allergies?

Scientists don’t entirely know why someone might suddenly develop a new allergy. But because the immune system is constantly changing and evolving, it’s always possible to develop a new allergy to familiar things, according to Greenberg.

On the contrary, it’s impossible to develop an allergy to something the immune system has never been exposed to before. But the immune system can sometimes react to certain proteins that are sufficiently similar to other allergens.

People who have atopic dermatitis (eczema) might be more prone to food allergies than those who don’t have it, according to Jenna Podjasek, MD, an allergist and immunologist based in Illinois. Scientists have theorized that the disruption of the skin barrier could contribute to allergen exposure via breaks in the skin.

“The risk of food allergy comes down to a combination of genetics, what foods we are exposed to and when, and how permeable the barriers in our gastrointestinal tract and skin are to allergens,” Podjasek told Verywell.

Contrary to popular belief, you can’t really develop food allergies just because you ate too much of something, according to Greenberg. But Podjasek said there are some isolated cases where there’s a clear relationship between repeated exposure and subsequent allergen sensitization.

“For example, repeated stings of a particular jellyfish in Japan may cause an individual to develop an allergy to soybean,” Podjasek said. “The allergen introduced into the body during the sting is thought to trigger a cross-reaction with the same or similar substances found in soy.”

Some have pointed to climate change as a reason for the uptick in adult allergies, and it has contributed to worsening symptoms in people with chronic respiratory allergic diseases such as asthma and hay fever. This is because climate change has increased the intensity of the pollen season and prolonged its duration. But so far, Greenberg said, there’s no evidence that it plays a role in food allergies.

How Do You Know Whether You’re Allergic or Sensitive to Certain Foods?

You may know someone who can’t eat gluten in North America, but went on a trip to Italy and claimed they could eat pizza and pasta to their heart’s desire without issue. While differences in grain quality or processing may impact someone’s ability to digest said food, this resembles food sensitivity rather than an allergy.

For instance, someone with celiac disease (gluten allergy) will be allergic to all gluten regardless of geographic location, Greenberg said.

A food allergy is an immune response that typically occurs minutes, or a maximum of three hours, after ingesting a specific food. Allergic reactions may involve varying symptoms, such as hives, swelling, and redness. Severe reactions, called anaphylaxis, can result in fatal respiratory problems.

Meanwhile, food sensitivity typically affects the gastrointestinal system and is often subjective. It doesn’t carry the same level of risk as the symptoms of a food allergy. For example, dairy sensitivity or intolerance may cause bloating, diarrhea, or pain, but not wheezing or anaphylactic shock.

If you suspect you may have a new allergy or food sensitivity, Greenberg recommends keeping track of your recent food history to identify possible triggers.

“What were the first symptoms and how did the symptoms evolve over time? What was ingested, including medications, in the hours leading up to the reaction?” he said. “If possible, get an ingredient list of what created the reaction.”

Getting a skin prick test or blood test can also help confirm a food allergy diagnosis.

Related:Best At-Home Allergy Tests

Can You Outgrow Adult-Onset Food Allergies?

As a whole, peanut, tree nut, and shellfish allergies are less likely to be outgrown than milk, egg, and wheat, according to Podjasek. But unfortunately, allergies developed in adulthood are unlikely to resolve or be “outgrown” in time, as are childhood allergies that persist into adulthood.

“Although no peer-reviewed studies address this question, it would be very rare for an adult-onset food allergy to resolve,” Podjasek said. “But of the adult-onset group, the majority are diagnosed by age 40 or younger. So our risk of developing a food allergy decreases significantly as we age.”

If you suddenly experience an allergic reaction to a food you've eaten throughout your life, it might be an adult-onset allergy. You can try to keep track of what you've eaten and your symptoms, and you can visit an allergist for further diagnosis and treatment.