12 Foods That Can Cause An Itchy Roof of Mouth

Medically reviewed by Daniel More, MD

If you’ve noticed that after eating certain foods, you have an itchy roof of mouth for a few minutes, you might have oral allergy syndrome (OAS), also known as pollen food allergy syndrome (PFAS). This condition is the most common food allergy in adults.

OAS is characterized by mild itching and swelling in your mouth, lips, tongue, or throat. Most people feel the symptoms start a few minutes after eating a certain food but sometimes it can take up to a half hour.

Typically, OAS happens in people who are allergic to pollen. There are proteins in certain foods that are similar to proteins in pollen, and your immune system gets confused and mounts an attack. Once the food makes contact with your mouth, an immune response happens. OAS is usually a mild allergic reaction, but in rare cases it can be serious.

OAS usually happens when you’re experiencing allergic rhinitis, also called hay fever or just seasonal allergies. Allergies happen because your body releases histamine, an immune system chemical that causes symptoms of allergies. If your immune system is already geared up from pollen, eating certain foods that contain similar proteins can also make your mouth and throat feel itchy. 

Some foods are more likely to trigger OAS than others. Eating the canned version of OAS-triggering foods can limit your body’s reaction.

Here are 12 common foods that have similar proteins to pollen.

Related: Allergies That Might Seem Surprising

Apples

Apples and birch tree pollen have similar proteins, so if you have a birch tree allergy, you could also have some sensitivity to apples—maybe some types more than others. Birch trees grow in all 50 states and tend to pollinate in the first few months of the year.

Some people notice that Granny Smith apples make their mouth itch more than other apple varieties, but not everyone. Fuji apples may cause less of a problem, but most people who have OAS with apples either avoid them all or find a variety that doesn’t bother them as much.

Melons

Millions of people are allergic to ragweed, a weed that grows in all 50 states. Because the proteins in the ragweed pollen are similar to proteins in melons, there can be a crossover reaction. Cantaloupe, honeydew, and especially watermelon can cause an itchy roof of mouth for people with seasonal allergies.

Watermelon can also cause an itchy roof of mouth for people with grass allergies, like orchard grass and Timothy grass. If you have hay fever from ragweed or grasses—and especially if you have both—it may be best to avoid watermelon.

Zucchini

Ragweed pollen and zucchini have similar proteins, so if you’re allergic to ragweed, zucchini may also pose a problem. Zucchini is usually eaten cooked, so if your allergy is mild, zucchini may still be okay to eat as the cooking process breaks down the protein.

The allergen-producing proteins are often in higher concentrations in the peel, so peeling the zucchini first may help reduce your allergic reaction or help you avoid symptoms altogether.

Bell Peppers

Bell peppers come in a variety of colors—from green, red, orange, yellow, and even white and purple —but they all have one thing in common. They contain proteins that are similar to a common weed called mugwort and can cause itchiness and swelling in people who have a seasonal mugwort allergy.

Peeling a fruit or vegetable before eating it can often cut down on the allergic reaction it may induce, but bell peppers are difficult to peel. However, they can be cooked, which should decrease or eliminate any reaction.

Oranges

Oranges have similar proteins to grass pollens and can cause symptoms of allergic rhinitis. This may occur with different types of oranges, like clementines, tangerines, mandarins, blood oranges, and others.

While OAS can happen with any kind of plant food, oranges are the citrus fruit most likely to cause symptoms. Other citrus fruits like lemons, limes, and grapefruit aren’t usually as problematic. Most of the proteins are in the peel, which usually isn’t eaten. However, some dishes use orange peel, so make sure to watch out for that, since the peel can cause more of a reaction.

Cruciferous Vegetables

Cruciferous vegetables like broccoli, cauliflower, and cabbage are being studied for their cancer-fighting compounds. Unfortunately, they can also cause allergic reactions in people with mugwort pollen sensitivities because cruciferous vegetable proteins are very similar to mugwort pollen proteins.

The good news is that most of the protein is broken down by cooking. If raw cabbage, cauliflower, broccoli, or any other cruciferous vegetable causes your mouth to itch, try cooking them. The cooking process denatures the protein, breaking it down so your immune system may not recognize it.

White Potatoes

Both ragweed and grass pollen proteins are similar enough to those in white potatoes, so if you're allergic to ragweed and grass pollen, eating white potatoes can cause your immune system to react.

However, thankfully, potatoes usually don’t cause issues because they aren’t often eaten raw. Cooking potatoes destroys enough of the protein that it causes less of an allergic reaction. Peeling the potato can be even more helpful. Even though a lot of the nutrition is in the skin, if you peel it, you are getting rid of most of the allergen-causing proteins. Some people experience itchy hands that turn red and swell when they peel white potatoes.

Garlic and Onion

Both garlic and onions have proteins that are similar to mugwort pollen. If your rhinitis is caused by mugwort, you may also feel an itchy mouth when eating garlic and onion.

Cooking both garlic and onion can help, since cooking denatures the proteins, rendering them less effective. As long as your OAS is mild, you can try eating these vegetables when they’re cooked to see if you can tolerate them. Allium vegetables, like garlic and onion, are associated with tremendous health benefits and have plant compounds that fight cancer, reduce inflammation, and improve metabolic health.

Bananas

Fruits commonly grown in tropical environments, like bananas, can trigger OAS symptoms. The protein found in bananas is similar to the protein in ragweed, causing an immune system reaction in people with seasonal ragweed allergies.

Much of the protein is found in the peel, which is good news, because the peel isn’t usually eaten. Banana peels are edible, but usually avoided. Unfortunately, drying the banana and eating it as a chip doesn’t reduce the amount of protein in it.

Tomatoes

If you have seasonal allergies to birch, cypress, cedar, or grass, you may feel a reaction to tomatoes. All of these plants have similar proteins and eating raw tomatoes can cause an immune response, like an itchy mouth or runny nose.

Tomatoes, and other red vegetables and fruits, are a rich source of lycopene, a carotenoid with numerous health benefits. This nutrient acts as an antioxidant and can help reduce oxidative stress associated with type 2 diabetes. Try cooking tomatoes to get the health benefits while also reducing the chance that you’ll have a reaction.

Pineapples

If you live in an area with oak, mesquite, and ash trees, and you have seasonal allergies to their pollen, you may also react to pineapples. Like others on this list, they have very similar proteins that cause immune system reactions. Studies show that pineapple is a common source of OAS in children.

Pineapples are also known to cause a burning or tingling sensation on your tongue, which is different from OAS. This tingle is caused by bromelain, a collection of enzymes that pineapple contains. These enzymes break down proteins and cause a sore tongue.

Spices

It’s not just fruits and vegetables that can trigger OAS. Some spices have similar proteins to mugwort and can cause the same type of itching and swelling. These spices include aniseed, coriander, fennel, parsley, caraway, and black pepper. 

If you like using these spices but find that they cause itchiness, try using dried spices instead of fresh, raw spices. Avoiding the raw version of any of these foods can help cut down on the amount of protein that you’re ingesting.

Why Do Some Types of Food Make Your Mouth Itchy?

Many different types of fruits and vegetables contain proteins that are nearly identical to proteins found in pollen. Your immune system can become confused by their similarity, and begin to produce histamines to fight the allergen. If you’re already experiencing hay fever symptoms from pollen in the air, eating food with a similar protein can make your symptoms worse. This is called cross-reactivity.

It’s important to note that itchiness after eating nuts can be a sign of a more serious allergic reaction. While some nuts and legumes, like soybeans, peanuts, hazelnuts, and almonds may be associated with a birch pollen allergy, itchiness may also indicate something more serious.

If you experience an itchy mouth or throat after ingesting nuts (including peanuts), reach out to an allergist or immunologist. Nut allergies can be serious and should always be seen by a healthcare provider.

A Quick Review

Oral allergy syndrome is common in adults, and possibly becoming more common in children. There is no test for OAS, but it’s typical for people with OAS to have received a positive skin or blood test for seasonal allergies. If you have a history of feeling an itchy mouth, lip, tongue, or throat after eating a certain food, you may have OAS. Even if the effect seems mild, it’s always a good idea to seek advice from a healthcare provider.

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