HomeFood allergy basicsFood allergy 101What is food allergy?Oral Allergy Syndrome (OAS)/Pollen Food Syndrome (PFS)

Oral Allergy Syndrome (OAS)/Pollen Food Syndrome (PFS)

With OAS or PFS, the proteins in certain fresh fruits, vegetables and tree nuts are similar to those in pollens and can cause allergic symptoms.

Selection of healthy rich fiber sources vegan food for cooking

Oral Allergy Syndrome (OAS), now usually called Pollen Food Syndrome (PFS), is considered a type of food allergy. 

With OAS/PFS, the proteins in certain fresh fruits, vegetables and tree nuts are similar to those in pollens, and this “cross-reactivity” can cause allergic symptoms like itchiness of the mouth and throat. People with PFS are allergic to pollen, but sometimes the pollen allergy is mild. 


The symptoms of OAS/PFS are usually itchiness of the mouth and throat when eating fresh fruits or vegetables and/or nuts related to the pollen to which you are allergic. Occasionally, swelling of the lips, tongue, mouth or throat can occur. Examples of some of the fruits, vegetables and nuts that are similar to certain pollens are listed in our pollen allergy & foods chart

Symptoms typically develop within a few minutes of eating. Although it is uncommon, OAS/PFS can lead to anaphylaxis. OAS/PFS can occur at any time of the year, but symptoms may be worse in the cross-reactive pollen season.


Allergists can review a patient’s history and may perform different tests to confirm OAS/PFS, such as skin prick tests to certain pollens as well as the foods causing the symptoms. If you think that you or you child may have OAS/PFS, a referral to an allergist can help you obtain a formal diagnosis.

Managing OAS/PFS

Usually, people with OAS/PFS avoid the fresh or raw food causing symptoms. They can often tolerate the food if it is well cooked or heated because preparing the food with heat changes the protein composition of it. Canned foods can also be an option, and some find that peeling the offending fruit or vegetable is helpful. It is not necessary to avoid all foods that can cross-react if they can be eaten without symptoms. Plus, symptoms can be very specific to certain types of fruits and vegetables. For example, some may only react to one apple variety and not to another.  

In cases involving more than a little itching in the mouth/throat or symptoms to nuts, an allergist may recommend that you avoid certain food and carry an epinephrine auto-injector.

Learn more