Why Do Raw Apples Cause Your Mouth to Itch?

Oral allergy syndrome is linked to apples and other fruit

Woman selecting fruit at grocery store
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If you’ve ever bitten into an apple and felt your lips and mouth itching, tingling, stinging, or swelling, you may have a condition known as oral allergy syndrome (OAS). OAS is the result of an allergic reaction to a particular type of pollen that's found in apples, and is similar to a type of pollen found in birch trees.

All plants have pollen, which is how they reproduce. Every pollen you encounter is different; it is comprised of a unique set of proteins known as allergens.

If you are sensitive to a particular allergen, such as the one found in birch pollen, you will have an allergic reaction. Surprisingly enough for those who are allergic to birch pollen, some fruits contain a similar combination of proteins. If you bite into one of these fruits, you will also have an allergic response (albeit slighter and shorter lasting). This is oral allergy syndrome.

Cross-Reactivity of Different Allergens

Apples share similar proteins to the allergens found in birch pollen. This shared allergic response is called cross-reactivity. Other fruits, vegetables, spices, and nuts have similar cross-reactivity issues involving types of pollens, such as:

  • Birch and celery
  • Birch and almond
  • Birch and garlic
  • Cypress and peach
  • Mugwort and peach
  • Mugwort and bell pepper
  • Mugwort and coriander
  • Orchard grass and tomato
  • Ragweed and melon
  • Ragweed and cucumber

More than 50% of people with birch pollen allergies will react to raw apples. However, if you cook or process the apple—as you would when making applesauce or pie—those proteins get broken down. When this happens, your body no longer recognizes the apple as an allergen, and you won't have an allergic reaction.

The same applies to any other fruits, vegetables, spices, or nuts with known cross-reactivity. It doesn't matter if you choose an organic or non-organic product, an allergy will occur either way.

Symptoms of Oral Allergy Syndrome

Symptoms of OAS are usually confined to a local reaction of the mouth, lips, or tongue. They tend to be mild, more surprising than irritating, and last only a few seconds or minutes until the enzymes in saliva break the proteins down.

OAS is not a true food allergy but rather the body’s response to something it mistakenly believes is pollen. Very few people with OAS have a true allergy to the fruits or vegetables they eat. If they did, they would likely experience more pronounced symptoms including rash, abdominal cramps, diarrhea, or, in very rare instances, anaphylaxis (a potentially life-threatening allergic reaction).

People with OAS tend to have worse symptoms during allergy season when their bodies are already struggling with airborne pollens. For this reason, if you can otherwise tolerate raw fruits and vegetables and then suddenly you have a reaction, it might be because pollen counts are high.

Treating Symptoms of OAS

Allergic reactions limited to your mouth and lips can be treated with an over-the-counter antihistamine such as Benadryl (diphenhydramine). In most cases, you probably won’t need medication, since the OAS symptoms typically subside within minutes.

If you experience an unexpected food allergy, you should be monitored for a few hours on the off-chance a more severe reaction follows. This is especially true if it’s the first time you've had a reaction. In the event of anaphylaxis, you may experience:

  • Wheezing or shortness of breath
  • Hives or swelling under the skin
  • Facial swelling
  • Nausea or vomiting
  • Rapid heart rate
  • Swollen tongue
  • Mental confusion

If any of these symptoms occur, call 911 and get to the emergency room quickly. Anaphylaxis is always considered a medical emergency and, in most cases, is completely treatable if addressed quickly. If left untreated, respiratory asphyxiation (where the air passages close up), shock, and even death may occur.

If you have severe hypersensitivity, you doctor will likely have you carry an epinephrine auto-injector (EpiPen) in the event of an emergency.

A Word from Verywell

If you've experienced oral allergy symptoms, you should know that pollen is not the only allergen connected to OAS. Latex allergies, which affect about 5% of people, are associated with allergies to avocados, bananas, chestnuts, kiwis, and papayas.

If you are allergic to apple cider or cider vinegar but not to raw apples themselves, you may be allergic to brewer’s yeast, a byproduct of fermentation, as opposed to having OAS. 

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Article Sources
  • NIAID-Sponsored Expert Panel: National Institute of Allergies and Infectious Diseases. “Guidelines for the Diagnosis and Management of Food Allergy in the United States: Report of the NIAID-Sponsored Expert Panel.” Journal of Allergy and Clinical Immunology.