Oral allergy syndrome may progress to systemic symptoms in 8.7% and anaphylactic shock in 1.7%

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.

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

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

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.

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.
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
In birch-apple syndrome (oral allergy syndrome), eating apple does not affect the respiratory tract. Annals of Allergy, Asthma and Immunology, 2011.
Image source: Head and neck. Wikipedia, public domain.


  1. James Thompson5/11/2010

    For birch sensitive patients It would be difficult to avoid all fresh fruit and vegetables. Immunotherapy such as SLIT can reduce the risk of systemic reactions to environmental and food allergens.

  2. Anonymous5/11/2010

    The above statement is misleading. SLIT is not yet proven as treatment for food allergy. In addition, birch sensitive patients obviously do not need to avoid "all fresh fruit and vegetables".

  3. James Thompson5/11/2010

    Well of course SLIT works well on food allergies, even serious peanut and tree nut allergies. Very safe, very effective and the cost is about a buck a day for treatment.
    Laubach S, et al. J Allergy Clin Immunol. 2008: 121:S96
    Enrique E et al J Allergy Clinical Immunol 2005;116:1073-1079

    So most fresh fruit and vegetables have the Bet v1 homologue PR-10, a panallergen in carrots, celery, apples, pears, peaches, cherries..... Patients who are birch sensitive have more oral allergy symptoms during the spring tree pollen seasons. It is best to cut back on these foods during peak times. Foods which contain PR-10s can precipitate the same spring allergy symptoms as when eating a lot of apples in the fall. As far as birch sensitive patients go, an apple a day does not keep the doctor away.