Food allergies can make every moment, such as eating at a restaurant, attending a party or packing your child’s lunch, feel uncertain. For people who suspect they may have a food allergy, getting the right diagnosis is an important first step toward staying safe and gaining peace of mind. Symptoms of a food allergy can range from mild itching or an upset stomach to more serious reactions. Understanding what is causing those symptoms helps guide the next steps.
The AMA’s What Doctors Wish Patients Knew™ series gives physicians a platform to share what they want patients to understand about today’s health care headlines.
In this installment, two physicians took time to discuss what patients need to know about food allergies. They are:
- Amber Burnette, MD, an allergist and immunologist in Garden Grove, California, at Southern California Permanente Medical Group and assistant area medical director for Kaiser Permanente Orange County.
- Zachary Rubin, MD, a pediatric allergist and immunologist in Oak Brook, Illinois.
Southern California Permanente Medical Group is part of the AMA Health System Member Program, which provides enterprise solutions to equip leadership, physicians and care teams with resources to help drive the future of medicine.
Food allergy diagnosis starts with a detailed history
“The most important part of a food allergy diagnosis is not the test. The most important part is the history, the story. What happened? What did you eat? How long after did you develop symptoms?” said Dr. Burnette. “The history's more important than anything else. And the testing is used to help either confirm or rule out things.”
“A detailed history is necessary because if you just test or get an at-home test, it's not nearly as accurate,” said Dr. Rubin. “We often refer to this as the pretest probability. So, before you get a test, what's the likelihood that this test is going to answer the question that I'm looking for?”
“It's relatively low if you just test without getting a history. So, we need that story,” he said. “For example, you consume peanut butter and then immediately get hives. Especially if that's happened multiple times, that's likely an allergy.”
A skin or blood test confirms a food allergy
“We can do testing either via skin testing, which is what most people are used to, or blood testing,” said Dr. Burnette. “Either way, we’re looking for that same IgE allergy chemical marker because that’s what mediates immediate-type allergic reactions.”
“The blood tests are very accurate, more so than they used to be, so some allergists only do blood testing now,” she said. “Then the skin test is of the older testing modalities. You put the little drops in your skin, wait 15 minutes to see if you get a hive—a little itchy bump there—and see if that matches up with the history.”
The gold standard test is an oral food challenge
“The gold standard test for food allergies is something called an oral food challenge,” said Dr. Rubin. “In the clinic, under a medically supervised setting, you're eating small but incremental doses of the food that you're worried about to see if you react.
“An allergist will then watch that patient carefully to see if they actually react,” he added.
Food sensitivity tests aren’t accurate
“With at-home tests, the biggest thing to know is often they are not testing IgE. They’re often testing something called IgG, which is another immune system chemical antibody. It’s not a marker for an allergy. It’s a marker for tolerance,” Dr. Burnette said. “Everything you eat, you have IgG for, because your body puts a flag to say it isn’t dangerous.”
“If you do an IgG at-home test, they’re going to test you for 50 different things. It’s usually a couple hundred dollars, and it’s going to come back with all these random levels that mean nothing because you’re not allergic to those foods, which is not helpful,” she explained.
“I'm seeing overdiagnosis of food allergies where people get a food sensitivity test that's not really an allergy,” Dr. Rubin said. “People come in thinking that they're sensitive or allergic, but in reality, it's just a meaningless test.”
For example, a positive test for coffee when the patient drinks it regularly, he said. “It just means you're exposed to the food. It doesn't actually mean that you're truly sensitive or allergic. It's just a way for our bodies to understand that food is safe.”
An itchy mouth after eating may be oral allergy syndrome
“If you have a mild itching in your throat, usually with fresh fruits or vegetables, there's another condition called oral allergy syndrome,” said Dr. Burnette. “Oral allergy syndrome is an allergic reaction caused by cross-reactivity between pollen and certain raw fruits, vegetables or nuts.”
“It’s a pollen allergy, but your body thinks that you’re eating the plant that you’re allergic to when you eat a fruit or vegetable that’s chemically similar to it,” she explained. “For example, avocados can be related to some of the tree pollens, typically birch trees. Apples cross react with birch trees, too.”
“Often people will experience the oral itching with apples, and when we test them, we find an allergy to birch trees. Certain melons will cause it too,” Dr. Burnette said. “Oral allergy syndrome is very mild. It might be a little itching in your throat because you’re getting a couple little hives in your mouth that are short-lived and go away on their own.”
“Drinking water or taking an antihistamine and being aware of it and avoiding whatever form of the fruit or vegetable causes it, is the treatment for that,” she said. “But if every time you eat an apple of any sort, you break out in hives and start swelling up or start feeling your throat closing up, that’s anaphylaxis, not oral allergy syndrome. You will need to avoid that food and carry epinephrine.”
Introduce allergenic foods early
“We know that the timing of introducing foods plays a role in food allergies. That’s why our guidelines changed,” Dr. Rubin said. “Back in 2015, after a major study called the LEAP study—Learning Early About Peanut study—came out, we realized that when you introduce peanut before 1 years old, you decrease the risk of developing a peanut allergy by around 80% compared to if you introduce it at 5 years old, for example.”
“A decade before the study was started and published, the incidence of peanut allergy had tripled in westernized countries and they wondered, ‘OK, what’s going on here?’ And they started looking at countries where that wasn’t the case,” Dr. Burnette said. “What they found is that usually they were exposing their infants to peanut really early, whereas in the U.S., back in the early 2000s, we would tell them not to give them those foods until they’re 3.”
“The biggest thing that we do now, knowing that there is no current cure for food allergies, is doing what we can to prevent them by starting exposure early,” she said. “We counsel our families to introduce peanut and other allergic foods as soon as the child’s ready to tolerate it—sitting up, has good stomach control and can eat the food. We start as early as 4 or 5 months for peanut and eggs and then start other foods.”
Test one food at a time
“There are these companies that make infant food pouches where they mix all of the food allergens together for testing allergies,” said Dr. Burnette. “As an allergist, we don’t love that. We do want them to get exposure, but it is better to do one food at a time.”
“If they have a reaction and they have had seven different foods, we don’t know what caused it. Then, they have to come in and be tested for every food they ate,” she added. “We usually counsel people to start early, with one food at a time, and slowly introduce new foods after a few days. That way, we can see if something happened and what caused it.”
The first line of treatment is epinephrine
“It is important to recognize the symptoms of anaphylaxis, which is a severe and potentially life-threatening allergic reaction,” said Dr. Burnette. “Symptoms may include shortness of breath, throat closure sensation, wheezing, hives or swelling, and sometimes also include vomiting.”
“The gold standard is avoidance of the known triggers, which we can help determine if they don’t know for sure,” she said. “Then carrying injectable epinephrine, which is the first line treatment for anaphylaxis.”
Echoing that, Dr. Rubin said, “You have to take epinephrine immediately at the first little sign that you notice. If you think you have a severe allergic reaction, you should always use it first and fast.”
“Then after five to 10 minutes, if you feel like you're not getting better or it's getting worse, you can use a second dose and you're calling 911,” he said, noting “the people who should have them are those who have had a history of anaphylaxis or have a known diagnosis to food allergies.”
“The biggest mistake is a delay in administration of epinephrine,” Dr. Burnette said. “People having severe reactions need to use their epinephrine immediately. Yes, it hurts for a second, but it works very quickly and it can save your life, and it will stop the reaction.”
Don’t leave epinephrine in the car
“A common mistake with epinephrine is leaving them in their car,” said Dr. Burnette. “It is a medication and they are temperature sensitive.”
“We tell people epinephrine should be at room temperature, so keep it with you,” she said. “Also, most epinephrine come with a training device, so we want to make sure that people are carrying the medicine and not the trainer. I've seen that before.”
Oral immunotherapy is another treatment
There is another treatment option for food allergies and “one is oral immunotherapy, or OIT,” Dr. Burnette said. “Allergies come from your immune system being hyperactive. OIT teaches the immune system to tolerate allergens you are allergic to.
“We’ve been giving allergy shots for over 100 years for people with nose allergies to help desensitize them from pollens,” she said. “This is a similar concept with tiny exposures helping to teach the immune system that it doesn’t don’t need to freak out and overreact to allergens.”
“Whereas allergy shots are shots given in the arm for foods, if you injected somebody with something they’re allergic to, they will go into an anaphylactic reaction. That’s not what we do,” Dr. Burnette said. “For food desensitization, it’s oral and it’s usually starting with tiny amounts of food. For peanut OIT, for example, if you go through the whole process—which takes about six months of gradually increasing the amount of food—you could get up to about one to two peanuts worth of peanut protein that protects you against accidental exposures.”
“It does not allow what’s called ‘free eating,’ where you could eat all the peanuts you want, but it does raise the threshold for a reaction,” she said, noting that “if you miss a few doses, you can revert back, so you always still have to carry epinephrine and be careful.”
There is also an injectable biologic medication
Another treatment option for food allergies is “an injectable biologic medication called omalizumab, also known as Xolair, which we’ve been using for allergic asthma and chronic hives,” Dr. Burnette said. “It’s the only medication treatment for food allergy, and their clinical trials show that getting injections with this medicine can decrease the risk of anaphylactic reactions by about two-thirds.”
“It’s not a cure and the effects last as long as you get the medicine,” she said. “When I am talking to families about this, they need to know that there are some side effects potentially associated with this medication, including headaches or muscle aches.”
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Inform your school about food allergies
“Depending on how many food allergies you have … a lot of times the schools will offer an individualized educational plan around their diet to help make sure that the food isn’t being served to a child with a food allergy,” said Dr. Burnette. “We’ll fill out these food and meal accommodation forms so they can substitute the food” or avoid it.
“Some schools go as far as having allergy-free tables or have policies where families can’t send peanuts or tree nuts,” she said. “In a school environment, it’s very important for parents to talk to the school so everyone can understand how the school can help support. Then there are also all kinds of family support groups online to help families manage food allergies in the school setting, while traveling and everywhere else.”
Food allergy labeling is not standardized
“When you see labels like ‘made in a facility with peanuts’ or ‘made on shared equipment that processes peanuts,’ it's completely reasonable to wonder whether one label is safer than the other,” said Dr. Rubin. “However, these types of labels—called precautionary allergen labeling—are not standardized or regulated in the same way as ingredient lists. Therefore, one label isn't necessarily more or less risky than the other.
“In general, these terms suggest a higher risk of cross contact during manufacturing and may increase the risk of having an allergic reaction,” he added. “The level of risk can vary significantly, so it is best to talk with your allergist about this issue.”
Be mindful of the effect on mental health
“There is a strong association between having a food allergy and developing mental health issues such as anxiety and depression. And that happens with most chronic diseases, unfortunately,” said Dr. Rubin. Patients with food allergies are also “at higher risk of lifestyle issues like bullying.”
“A lot of parents who have kids with food allergies report being bullied because a lot of people don't really understand what food allergies entail,” he explained. “Many people may feel unfairly inconvenienced because a smaller group of individuals could have a significant problem if they were exposed to those food allergens.”
Always be cautious about food
“Always ask and just be cautious. If you don’t know, it’s better not to eat that food,” Dr. Burnette said. “For example, bake sales or parties. Sometimes people aren’t sure, so it’s better to not eat those kinds of foods.”
“The important thing is being aware of places you're most likely to encounter that food you’re allergic to,” she said, “and making sure that people who are serving you food or people around you know about your allergy.”
