Have you noticed food allergy warnings at restaurants? Maybe you’ve heard about peanut-free classrooms and flights. People who have serious reactions to certain foods must be careful about what they eat, and what others eat around them. There’s no cure for food allergies. But researchers are learning more about how to prevent and treat this condition.

Allergic reactions happen when your immune system—your body’s defense against germs and foreign substances—overreacts to something that’s normally harmless. In the United States, most food allergies are caused by peanuts, tree nuts, fish, shellfish, eggs, milk, wheat, and soy. Allergies show up most often in children. But they can develop at any age.

Food allergy symptoms can range from mild to severe. Some people experience a life-threatening reaction called anaphylaxis. Symptoms may include trouble breathing, dizziness, and fainting. When you have a food allergy, there’s no way to predict how your body will react when you’re exposed. You might have a mild reaction one time and a severe reaction the next.

If you think that you or your child may have a food allergy, see your health care provider. Your doctor will take a detailed medical history and perform a physical examination. If a diagnosis of food allergy seems likely, they may recommend a blood test or skin prick test. These results will help determine if you or your child has a food allergy.

NIH researchers have been working to better understand food allergies. “There has been a lot of research on peanut allergy because it is often severe, lifelong, and has a huge impact on quality of life,” explains Dr. Scott Sicherer, a pediatric food allergy expert at Mount Sinai’s Icahn School of Medicine. Scientists hope the progress they make on peanut allergy will help guide how to handle other food allergies.

Researchers recently carried out a large clinical trial called Learning Early About Peanut Allergy (LEAP). The study looked at infants’ chances of developing an allergy if they ate peanut-containing foods at an early age. Six hundred and forty infants who were at high risk of developing a peanut allergy were enrolled in the trial. The infants were randomly placed in either a peanut-eating or peanut-avoiding group. They continued these diets until they were 5 years old. Infants who ate peanut-containing foods beginning early in life had an 81% lower chance of developing a peanut allergy.

“Based on the strength of these findings, an expert panel sponsored by NIH recently issued updated guidelines to help health care providers work with families to introduce peanut-containing foods to infants to help prevent the development of peanut allergy,” Sicherer says.

The panel provided 3 guidelines that describe when and how to give these foods. The recommendations are based on how likely a baby is to develop peanut allergy. Talk with your doctor before you introduce any peanut-containing foods to your infant. The doctor may tell you when and how to start feeding peanut to your baby or recommend doing allergy testing first.

“It’s important to understand that these guidelines are about preventing peanut allergy, not treating an existing peanut allergy,” Sicherer explains.

The new guidelines may come as a surprise to some people. Almost 20 years ago, experts recommended that babies at high risk for developing peanut allergy avoid peanut-containing foods until age 3. But nearly 10 years ago, experts withdrew this recommendation. There was no proof that it worked.

“The most recent change in guidance was prompted by the very compelling results of the LEAP study,” says Dr. Marshall Plaut, a food allergy expert at NIH. “The new guidelines are based on these results and the clinical knowledge of the expert panel who developed them.”

Whether this strategy works for other food allergies isn’t known. “More research is needed to find out if early dietary introduction of other foods may help prevent allergy to those foods,” Sicherer explains.

NIH scientists are also looking at ways to treat people who already have food allergies. One promising strategy is called oral immunotherapy. It involves eating small, slowly increasing amounts of the allergy-causing food. One recent study tried this approach for peanut-allergic preschool children. Almost 80% of children given the treatment could safely eat peanut-containing foods afterward. More studies are being done to improve the safety and effectiveness of the approach. The therapy is also being studied for people with milk and egg allergies in small clinical trials.

There may be other ways to provide this type of therapy. One ongoing study is investigating using a skin patch to deliver small amounts of peanut protein to peanut-allergic patients. Early results have shown some promise among young children with peanut allergy. Researchers will continue to assess this approach.

Food allergy studies have to be done very carefully because reactions can be life threatening. “It’s important to understand how much careful thought goes into ethically designing research studies, particularly those involving vulnerable populations like children,” Plaut says. “Sometimes answers take longer than we would all like. But it’s critical to find them in a way and at a pace that is thoughtful and safe.”

For now, there are no treatments for food allergies. But avoiding allergy-causing foods can help prevent symptoms. Read food labels carefully. Wash your hands and surfaces you touch to prevent accidental contact.

Sometimes it can be difficult to avoid exposure completely. Carrying an epinephrine auto injector can be lifesaving. This device delivers a hormone that maintains blood pressure and can open your airways.

Talk with your health care provider to learn more about preventing and treating food allergies.

Food Allergy Symptoms

Pay attention to how you feel after you eat and learn how to recognize the symptoms of a food allergy.

Symptoms may include:

• coughing
• tingling in the mouth
• skin reactions like hives or itching
• nausea and vomiting
• stomach pain
• diarrhea

If you have a potentially life-threatening reaction—trouble breathing, dizziness, and fainting—seek immediate medical care by calling 911.

The gold standard for diagnosing food allergy is an oral food challenge. In this procedure, a food is eaten slowly, in gradually increasing amounts, under medical supervision to accurately diagnose or rule out a true food allergy. However, physicians use oral food challenges cautiously because the procedure is time-consuming, requires highly trained personnel, and can cause an acute allergic reaction.

The most frequently used food allergy diagnostics are the allergy skin-prick test and the allergy blood test. In a skin-prick test, a lancet is used to prick the skin under a drop of allergen extract. If a person is allergic to the allergen, a raised red bump will appear at the site of the prick after about 15 minutes. An allergy blood test measures the level of a type of antibody called immunoglobulin E (IgE) that is specific to a particular food or a protein within the food. People who have a food allergy make more IgE than normal to that food or protein.

Unfortunately, the results of these tests may indicate that a person has a food allergy when they really don’t—a result known as a false positive. A physician may consequently place an individual on an unnecessarily restrictive food-elimination diet, which can lead to poor weight gain, malnutrition, and reduced quality of life. This is an issue especially for people with atopic dermatitis, who are likely to have high total IgE levels and positive skin-prick or blood tests for foods but may not necessarily have a food allergy.

To avoid such misdiagnoses and poor health outcomes, an NIAID clinical trial begun in 2019 aims to identify threshold IgE levels to peanut and milk or a component of these foods that predict whether a person has a food allergy. This would clarify when it makes sense to do an oral food challenge to make a definitive diagnosis. The participants in the NIAID trial are people with atopic dermatitis who have a high total IgE level and may have an allergy to milk, peanut, or both. The study is expected to continue through 2027.

A Next-Generation Allergy Blood Test

To improve upon the allergy blood test, Pamela A. Guerrerio, M.D., Ph.D., chief of the NIAID Laboratory of Allergic Diseases, co-created a diagnostic tool called AllerScan with collaborators at Johns Hopkins School of Medicine in Baltimore. By analyzing a much smaller blood sample than required for typical allergy tests, this technology may help distinguish food allergy from food sensitization and non-allergy and may be useful for monitoring a person’s response to allergy treatment. Food sensitization means a person has a positive IgE test to a food but can still tolerate that food in their diet.

AllerScan is unique because it zooms in on allergenic epitopes, or the specific points where anti-allergen IgE antibodies bind to the proteins of allergens. This is important because several epitopes within a protein can be responsible for IgE reactivity. AllerScan can tease out IgE antibodies from blood that react to any protein epitope identified to date as a food or environmental allergen.

To test the new technology, Dr. Guerrerio and colleagues used AllerScan to examine the blood of people who had either wheat allergy, wheat sensitivity, or no allergy. Common diagnostic tools frequently yield false positives for wheat allergy, most likely because of cross-reactivity with grass pollen allergens.

AllerScan detected that people with wheat allergy tended to have an IgE response to an epitope in a wheat protein called alpha purothionin. By contrast, people with wheat sensitivity or no wheat allergy had a strong response to the alpha purothionin epitope by a different type of antibody called immunoglobulin G (IgG), which is known to block the effects of IgE. Wheat-allergic individuals who subsequently underwent oral immunotherapy to treat their allergy had a reduction in the number of wheat protein epitopes to which IgE antibodies reacted and an increase in the number of wheat protein epitopes to which IgG antibodies reacted. These findings were reported in the journal Nature Communications in 2021.

Oral immunotherapy, or OIT, is being tested in several NIAID-funded clinical trials to evaluate the role of OIT in treating and managing food allergy. OIT involves eating small doses of the food that causes the allergy—usually in the form of a powder mixed with a harmless food—and gradually increasing these doses every day. A 2012 study from the NIAID-funded Consortium of Food Allergy Research (CoFAR) suggested that egg OIT can benefit children with egg allergy. Most of the study participants could be safely exposed to egg while on egg OIT, and some were able to safely eat egg after stopping OIT.

In 2017, a NIAD-funded study called MAP-X found that a course of an additional medication, an injectable antibody called omalizumab, taken during OIT improved the safety of the therapy in children with allergies to several different foods. More than 80 percent of children who received omalizumab and OIT could safely consume two-gram portions of at least two foods to which they were allergic, compared with only a third of children who received placebo and OIT.

Now, in an ongoing NIAID-supported study known as OUtMATCH, researchers are testing the ability of biweekly or monthly injections of omalizumab—alone or together with multi-allergen OIT—to increase a person’s ability to tolerate multiple foods to which they are allergic. Investigators will enroll about 225 adults and children at 10 clinical CoFAR sites throughout the United States. Read more about OUtMATCH.

In epicutaneous immunotherapy, or EPIT, an allergen is delivered to the skin’s surface by a wearable patch. In 2016, CoFAR completed a study to evaluate the safety and efficacy of EPIT for peanut allergy. The therapy enabled recipients of the patch to tolerate larger amounts of peanut in a blinded oral food challenge after one year of treatment compared to the amounts they could tolerate in an oral food challenge at the start of the study.

For several allergy problems, like hay fever, health care providers may recommend subcutaneous immunotherapy, or allergy shots, in which allergens are injected directly into a person’s body. Researchers are no longer pursuing this approach as a treatment for food allergy because initial attempts too frequently caused severe allergic reactions.

Consumption of food that includes baked milk or egg products is a potential alternative to OIT for treatment of milk and egg allergies. Temperature-associated changes in certain milk and egg proteins may render baked versions of these foods less allergenic. However, the same does not hold true for all allergy-triggering foods. For example, roasting peanuts can make them even more likely to cause allergic reactions.

Studies have suggested that some children who are allergic to uncooked egg and milk can tolerate small amounts of these foods in fully cooked products such as muffins. One NIAID-funded study in 2011 found that more than half of baked-milk-tolerant children were able to tolerate foods containing uncooked milk after caregivers followed specific instructions to include baked milk products into their diets. The results also suggested that children who consumed baked milk outgrew their milk allergies more quickly than children who did not. However, many of the children treated with baked products were never able to eat unheated milk without allergic reactions. Additional studies are needed to determine how beneficial the baked food approach can be for certain people with food allergy.​​​