The Surprising Reason Your Mouth Itches After Eating an Apple

As if itchy eyes and a runny nose weren’t bad enough, if you have pollen allergies, you might also experience an unpleasant side effect when eating raw fruits and veggies. It’s called oral allergy syndrome or pollen-food allergy syndrome, and it’s a complex hybrid allergic reaction of sorts. You definitely need to know about it if, say, your mouth became itchy the last time you ate an apple.

Here’s what happens: If you’re allergic to birch tree, ragweed, or grass pollen, your body reacts to certain proteins in that pollen. Some raw plant foods contain very similar proteins that confuse your body, causing a local reaction in or around your mouth when you eat them, called cross-reactivity.

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Some experts consider it a mild food allergy, some consider it a pollen allergy, some people consider it both. “The body makes specific antibodies called Immunoglobulin E (IgE) against a particular protein,” explains Julie McNairn, MD, a specialist physician at Allergy and Asthma Associates in Ithaca, New York. “In the case of oral allergy syndrome, the antibody is against birch pollen, for example, not against apple. With food allergies, generally it’s made against a protein of that food.”

As many as 70% of people with pollen allergies also experience oral allergy syndrome symptoms after eating raw produce (and some nuts). Here’s what you need to know.

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Apples might be the food most likely to spark oral allergy syndrome symptoms, Dr. McNairn says. Along with other pitted fruits like apricots, cherries, peaches, and plums, apples are associated with birch pollen allergies—as are almonds, carrots, celery, hazelnuts, kiwi, parsley, and soybeans. Bananas, cantaloupe, cucumbers, honeydew, peppers, watermelon, and zucchini can cause oral allergy syndrome symptoms in people with ragweed allergies. And people with grass allergies might react to oranges, peaches, tomatoes, and more.

“What allergy you have determines what foods you’re more likely to have this reaction to,” says Tania Elliott, MD, an allergist in New York City and chief medical officer of preventive health company EHE.

While nuts can cause oral allergy syndrome symptoms, they’re more likely than other foods to cause severe food allergy symptoms, Dr. McNairn adds, so you’ll definitely want to bring up any nut-related mouth itchiness with an allergy doc. “If you’re not allergic to pollen, that makes a food allergy much more likely as well,” she says.

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People with oral allergy syndrome are likely to experience an itchy mouth or scratchy throat, itchy or slightly swollen lips, and in some cases, itchy ears. The symptoms typically start shortly after eating a problematic raw fruit or vegetable, but they’re also usually mild and go away within a few hours at most. “Oral allergy syndrome is usually harmless,” says Hannelore A. Brucker, MD, a member of the American Academy of Allergy, Asthma, and Immunology.

Enzymes in the digestive process break down the pollen-mimicking proteins in raw produce, so the symptoms usually remain local to the mouth. But in rare cases, oral allergy syndrome can become more severe, Dr. Brucker says. In fact, about 5% of people with oral allergy syndrome symptoms go on to have body-wide signs like nausea or vomiting, and some can even worsen to the potentially life-threatening anaphylaxis, which can include swelling, hives, and even shock.

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Severe reactions are rare and would require a great deal of exposure, Dr. Elliott says. “All of a sudden the body is totally overwhelmed by, say, a lot of apples and you’re ignoring the symptoms,” she explains. You're also more likely to have a severe reaction if you're highly sensitive to the pollen, Dr. McNairn adds. The more sensitive you are, the more likely it is that you'll react to a growing number of foods over time too.

While allergy symptoms like itchy eyes and a runny nose vary by season, oral allergy syndrome symptoms can crop up at any time of year, Dr. Brucker explains. However, if it’s a particularly bad pollen season for you, you might notice worse oral allergy syndrome symptoms as well, Dr. McNairn adds.

As with any allergy diagnosis, your doctor will first ask you about the history of your symptoms, Dr. Elliott says. Then a skin prick test or a blood test can help confirm the diagnosis and determine the specific pollen you’re reacting to. Skin prick tests can also test for food allergies, but in the case of oral allergy syndrome, “typically pollen will be positive and food will be negative,” Dr. McNairn says.

It’s possible you may not even realize you have a pollen allergy, Dr. Elliott adds. “Some people could have a very mild pollen allergy, and its main manifestation is pollen-food allergy syndrome. They might come to me saying they can’t eat fresh fruit because of their itchy mouth. I’ll say, ‘Do you get itchy eyes and a runny nose in the spring?’ And they’ll realize they do, every spring!”

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The most straightforward way to avoid oral allergy syndrome symptoms is to stop eating the foods you react to. However, with so many nutritious items that could land on your do-not-eat list, you certainly don’t want to ban all produce from your diet.

Here’s the good news, and another major difference between oral allergy syndrome and a more severe or true food allergy: You can usually eat these cross-reactive foods if they’ve been cooked. “Generally, you could eat apple pie, versus with a true food allergy, you wouldn’t be able to eat apple in any form,” Dr. McNairn says.

That’s because cooking—including microwaving or even some processing, like canning—breaks down the pollen-mimicking protein, Dr. Elliott explains, so your body no longer registers it as a foreign invader.

Some people with oral allergy syndrome find their symptoms are lessened if they first peel the offending fruit or veggie before eating it raw, Dr. Elliot says.

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If your pollen allergy symptoms are bad enough to warrant treatment with allergy shots, you might get the side benefit of becoming less sensitive to oral allergy syndrome as well. Allergy shots “make the body tolerant to what it’s allergic to,” Dr. Elliott says. Overtime, people can be effectively cured of their allergies, and some studies show improvement in oral allergy syndrome too, she says.