Fresh produce and itchy mouths, throats may indicate oral allergy syndrome

Key takeaways:

• Patients with hay fever or seasonal allergies caused by pollen may develop an itchy mouth or throat after eating fresh produce.
• Proteins found in some produce are similar to those found in some pollens.

Editor’s Note: In Healio Allergy/Asthma’s column, “Food Allergy: Fact vs. Fiction,” Douglas H. Jones, MD, breaks down what’s true and what’s myth for a variety of topics related to food allergies. If you have a question you would like answered in this column, email Jones at rmaaimd@gmail.com or Richard Gawel at rgawel@healio.com.

This time of year, I see many patients who complain of an itchy mouth with watermelon or fresh bananas or apples, and they really want to eat them on a summer’s day. They ask what can be done.

The first thing I ask is if they tolerate bananas in banana bread, but not raw or fresh. When they say they do, I am already locked in that what they may be experiencing is something called oral allergy syndrome (OAS), also known as food pollen syndrome.

This is a condition where the mouths or throats of people who suffer from hay fever or seasonal allergies caused by pollen may become itchy after eating fresh fruits or vegetables or even some nuts such as walnuts, almonds or hazelnuts. This happens in up to 50% to 75% of adults allergic to birch tree pollen.

Douglas H. Jones

Why does this happen? Basically, a person’s immune system gets tricked. The proteins found in some fruits and vegetables are very similar to those found in certain pollens. So, when we consume the fresh or raw forms of these foods, it can confuse the immune system and cause an itchy mouth or tongue, rash around the mouth, or upset stomachs.

When those foods are cooked or processed, as in the case of bananas in banana bread, the protein configuration in the banana changes and does not resemble pollen so much. Consequently, the immune system recognizes it as safe and does not confuse it with pollen and think that it is not safe. People can tolerate those versions fine.

However, this does not account for those individuals who have a separate and unique allergy to those foods, which can happen. It is critical that a detailed history be taken with proper validated testing and interpretation.

The most frequent symptoms of OAS include itchiness or swelling of the mouth, face, lip, tongue or throat. Occasionally, people can get upset stomachs as well. Symptoms usually appear immediately (or up to an hour later) after eating raw fruits or vegetables, certain nuts and even some grains.

The risk for severe allergic reactions such as anaphylaxis is slim, but not none. Rarely, severe swelling leading to difficulty swallowing or breathing can occur. OAS can occur at any time of the year, but it may be more prominent when pollen counts are high.

Food allergy testing often yields mixed results and may not correlate with history. As in any food allergy patient, the history is the most important part of the puzzle. Allergy tests may help identify those who may only have classical food allergy to the fruit or vegetable that is not necessarily cross-reactive with pollen.

The American Academy of Allergy, Asthma & Immunology offers information about pollens and cross-reacting foods in OAS as well as great tips for managing OAS that you can share with your patients, including:

• If you have symptoms of OAS, avoid eating these raw foods, especially during allergy season because in many patients, OAS worsens during the pollen season of the pollen in question.
• Eat the cross-reactive food either baked, processed or microwaved.
• Peeling the food before eating may be helpful, as the offending protein is often concentrated in the skin.
• Some studies have shown that treatment with allergy shots can improve the symptoms of OAS.

Patients also should be advised to talk to their physician if:

• Their OAS symptoms are causing significant throat discomfort.
• Their OAS symptoms are getting progressively worse.
• Their OAS symptoms are caused by cooked fruits and vegetables.
• Their OAS symptoms are caused by nuts.
• They develop systemic reactions after eating raw fruits or vegetables such as hives, vomiting or difficulty breathing.

Reference:

• Oral allergy syndrome (OAS). https://www.aaaai.org/tools-for-the-public/conditions-library/allergies/oral-allergy-syndrome-(oas). Accessed: July 7, 2023.

For more information:

Douglas H. Jones, MD, FAAAAI, FACAAI, is cofounder of Global Food Therapy, Food Allergy Support Team and OITConnect, the director at Rocky Mountain Allergy at Tanner Clinic, and a Healio Allergy/Asthma Peer Perspective Board Member. He can be reached at rmaaimd@gmail.com or on Instagram @drdouglasjones.