If you see a perfect apple at a farm stand, do you eagerly buy it? Or do you avoid it because you’re worried about an itchy mouth or throat? If you’re in the second group, you may have oral allergy syndrome (OAS).

OAS results from a pollen allergy and may also be called pollen-food allergy syndrome (PFAS). MyFoodAllergyTeam members often express confusion about what this condition is and how it will affect them.

“What on earth is oral allergy syndrome, and why does it matter?” one member asked. Another said, “Can I find out if anyone seriously knows anything about oral allergy syndrome? How serious is it? How much do I need to strip out of my diet to stop reactions?”

Read on to find out what OAS may mean for you and how it’s related to environmental allergens. We’ll also discuss how you might reduce symptoms of OAS and common treatments.

What Is Oral Allergy Syndrome?

OAS happens when you eat a fruit, a vegetable, or an herb that contains proteins similar to those in pollen. Your immune system may mistakenly react as if you’ve been exposed to the pollen allergen, even though you haven’t. This can be referred to as cross-reactivity.

Oral allergy syndrome happens when you eat a fruit, a vegetable, or an herb that contains proteins similar to those in pollen.

Researchers estimate OAS affects up to 70 percent of people who are allergic to pollen.

For most people with OAS, raw foods are the problem. Cooked fruits and vegetables don’t usually cause the same allergic reaction. Because cooking changes the protein characteristics of the food, it usually helps reduce allergic symptoms. Still, it doesn’t make every trigger safe. Nuts and some other plant foods can still cause reactions even when roasted or cooked.

For most people, the discomfort from OAS is brief and mild because the digestive process changes the food’s proteins. Most reactions stay in the mouth and throat, but rarely symptoms can become more serious.

Which Foods May Trigger an Oral Allergy Syndrome Reaction?

Different foods are linked to different allergens, so the ingredients that trigger your OAS symptoms are probably linked to your environmental allergy. Not all people with OAS react to all the foods associated with their allergies. Some of the more common allergens and their cross-reactive foods are listed below.

• Birch tree pollen — Peaches, pears, apples, cherries, nectarines, apricots, plums, prunes, kiwi, carrots, celery, parsley, peppers, potatoes, parsnips, hazelnuts, almonds, peanuts, soybeans, and walnuts
• Grass pollen — Peaches, melons, oranges, tomatoes, potatoes, and Swiss chard
• Mugwort pollen — Mustard, garlic, parsley, coriander, fennel, caraway seeds, onions, peppers, cabbage, carrots, broccoli, parsnips, and cauliflower
• Ragweed pollen — Watermelon, cantaloupe, honeydew melons, cucumbers, bananas, zucchini, artichokes, and chamomile tea

Some foods on the oral allergy syndrome chart (especially peanuts and tree nuts) can sometimes be involved in more serious reactions or a separate “true” food allergy. Readers shouldn’t assume every reaction to foods in the categories on this chart will be mild OAS.

What Are the Symptoms of Oral Allergy Syndrome?

If you’re experiencing an OAS reaction, the symptoms may seem similar to another type of food allergy at first. Symptoms may include:

• Itching, tingling, or swelling in your mouth, lips, tongue, or throat
• A sore or scratchy throat
• Hives on your mouth or lips

Different foods are linked to different allergens, so the ingredients that trigger your OAS symptoms are probably linked to your environmental allergy.

In rare cases, OAS symptoms may be severe and can even cause anaphylaxis — a life-threatening, severe allergic reaction to a particular allergen. Symptoms that indicate you may be having an anaphylactic reaction include:

• Trouble breathing or shortness of breath
• Swelling or tightness in your throat
• Rapid heart rate
• Coughing or wheezing
• Dizziness
• Difficulty talking
• Confusion
• Slurred speech
• Nausea, vomiting, or diarrhea
• Blue, gray, or pale lips, tongue, or skin
• Abdominal pain or cramps

If you experience anaphylaxis, immediately use your emergency food allergy medications, such as an epinephrine auto-injector. Then call 911 for emergency medical care.

Most people don’t experience anaphylaxis from OAS, but it’s important to work with your allergist to determine how severe your condition is.

How Is Oral Allergy Syndrome Treated?

The best way to manage OAS is to avoid the food that causes your reaction. “I have oral allergy syndrome, and my tongue will swell a little,” one MyFoodAllergyTeam member wrote. “When I feel it, I immediately stop eating that food.”

You may also avoid an OAS reaction by eating the allergen in cooked form and avoiding raw fruits and vegetables that trigger your symptoms. Some people find they can avoid symptoms by peeling the skin from fresh fruits or trying different varieties. For instance, if an Empress peach causes symptoms, a Madison peach may not.

The best way to manage OAS is to avoid the food that causes your reaction.

Because oral allergy syndrome symptoms are rooted in environmental allergies, you may wonder whether allergy shots (immunotherapy) may help you manage OAS. For instance, if eating a banana causes your symptoms, it may seem logical that shots to prevent ragweed allergies would eliminate that reaction. Some people have reported that immunotherapy reduced their OAS symptoms, but not everyone finds that it helps.

Some people with allergies carry emergency allergy medications, such as an epinephrine injector. Whether this is advisable depends on your personal risk and the symptoms you get when you have a reaction. You should discuss your risk with an allergist. In addition to carrying an epinephrine injector, you might consider having over-the-counter antihistamines handy for less serious reactions.

Speak With Your Doctor

Be sure to talk with your doctor if you have a reaction to any food. Your healthcare provider can perform allergy tests to evaluate whether you’re allergic to the food itself or if you’re experiencing oral allergy syndrome. They can also advise you on how to treat and prevent OAS symptoms.

Join the Conversation

On MyFoodAllergyTeam, people share their experiences with food allergies, get advice, and find support from others who understand.

How do you manage your oral allergy syndrome? Let others know in the comments below.