Pollen-Food Allergy Syndrome (PFAS) or Oral Allergy Syndrome (OAS)

Author: V. Dimov, M.D., Allergist/Immunologist and Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist and Assistant Professor at NSU

Oral allergy syndrome (OAS, pollen-food allergy syndrome) is contact urticaria of the oropharynx. OAS is caused by allergens in fruits, vegetables, tree nuts, and peanuts that are homologous to pollen allergens.

Oral allergy syndrome (OAS) occurs in patients with a prior cross-reactive aeroallergen sensitization and clinically presents with oralpharyngeal symptoms after ingestion of a triggering fruit or vegetable.

Although controversial, these symptoms may progress to systemic symptoms outside the gastrointestinal tract in 8.7% of patients and anaphylactic shock in 1.7%.

OAS's underlying pathophysiology may play a role in clinical presentation and outcome, depending on whether the cross-reactive protein is a heat-labile PR-10 protein, a partially labile profilin, or a relatively heat-stable lipid transfer protein. Profilin is an actin-binding protein involved in the restructuring of the actin cytoskeleton. It is found in all eukaryotic organisms in most cells.

PAS is caused by raw fruits or vegetables, cooked foods are well tolerated. There are a number of cross-reactive allergens in pollen and plant foods. The sequence is:

- primary respiratory sensitization to pollen

- then reaction to food ingestion

Typical cross-reactive associations:

BIRCH - Apple, peach, apricot, hazelnut, potato, carrot, celery
RAGWEED - Banana, cucumber, cantaloupe, watermelon, zucchini, cucumber
MUGWORT - Celery, onion, mustard, cabbage

Cross-reactivity in Pollen-Food Allergy Syndrome (PFAS) or Oral Allergy Syndrome (OAS) (click to enlarge the image).


Diagnostic testing is variable based on the underlying food tested, but fresh food skin prick test typically has the highest sensitivity.


Treatment centers on avoidance and the consideration of self-injectable epinephrine. Because of its relationship with a cross-reactive aeroallergen sensitization, subcutaneous immunotherapy and sublingual immunotherapy have also been therapeutically tried with mixed results.

In patients with OAS to apple, tolerance can be induced with consumption of apple - but OAS recurs on discontinuation (Allergy, 2011).

Which allergen cross-reacts with Bet v1 (birch)?

(A) Ara h1 (peanut)
(B) Mal d 1 (apple)
(C) Ara h3 (peanut)
(D) Bos d (milk)
(E) Gal d (egg)
(F) Hev b2 (latex)

Answer: B, apple. Pollen sensitizations linked to food allergies was first reported with birch pollen and apples 50 years ago.

For patients:

Do raw or fresh fruits leave you sneezing, sniffling and with an itchy mouth, lips and throat? You may have oral allergy syndrome.


Oral allergy syndrome: a clinical, diagnostic, and therapeutic challenge. Webber CM, England RW. Ann Allergy Asthma Immunol. 2010 Feb;104(2):101-8; quiz 109-10, 117.
Interactive Allergy Map by Greer Labs. Click your state to find region-specific, common airborne allergens there.
Profilin may be a pan-allergen among plants that crossreacts between pollen, fruits, vegetables and latex http://goo.gl/ZUPRQ
Birch-Apple Syndrome Treated with Birch Pollen Immunotherapy (Oral Allergy Syndrome) http://goo.gl/4cASx

Related reading

Oral symptoms from the ingestion of food in a patient with allergic rhinitis - AAAAI Ask the Expert, 2011.
In birch-apple syndrome (oral allergy syndrome), eating apple does not affect the respiratory tract. Annals of Allergy, Asthma and Immunology, 2011.

Published: 05/09/2010
Updated: 12/21/2012

No comments: