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What is Oral Allergy Syndrome?

If you have an allergy to pollen and experienced an itchy mouth and/or throat after eating fresh fruit and/or raw vegetables, you may have Oral Allergy Syndrome (OAS). OAS is a cross-reaction that can occur when someone who is allergic to pollen eats certain raw fruit, vegetables or some nuts. Your immune system identifies certain proteins within the food you’re eating as the same as pollen because they look identical. A cross-reaction occurs when the proteins in one substance (typically pollen) are similar to the proteins found in another substance (typically food). And because of this cross-reactivity between pollen and food, OAS is sometimes called Pollen-Food Allergy Syndrome (PFAS).

People affected by OAS can usually tolerate the same fruit or vegetables after they have been cooked because the proteins are distorted during the heating process - the immune system no longer recognizes the food.


OAS Oral Allergy Syndrome

Common Oral Allergy Syndrome Symptoms:

  • Scratchy throat
  • Itchy mouth or lips 
  • Swollen lips, tongue, or throat
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These symptoms could become worse during times of the year when the pollen counts are high (usually in spring or fall). And these symptoms can start occurring at any time, even if you’ve been eating the food for years without any problems.1


What Causes Oral Allergy Syndrome?

People with OAS typically have an allergy to birch trees, ragweed or grass pollen. OAS is not common in young children; it generally shows up later in life, for those who have already been eating the questionable fruit and vegetables for years without a problem.1

Some Oral Allergy Syndrome foods include:  

Am I Allergic?


You may think what you are experiencing is harmless, but it’s important to find out what’s causing your symptoms – your allergic triggers. A simple blood test—together with your medical history—can help identify underlying allergen triggers. Be sure to consult with your healthcare professional because learning what could be behind your symptoms may also help you avoid more serious problems in the future. 

Learn more about testing

  1. J Allergy (Cairo). 2015; 2015: 543928. Published online 2015 Nov 8. doi: 10.1155/2015/543928 PMCID: PMC4655061