The Oral Allergy Syndrome is a common disease entity amongst hay fever sufferers. It has more recently been renamed Pollen-Food allergy syndrome. In this condition, Hay fever patients sensitised to pollen develop oral allergic symptoms to certain stone fruits and vegetables.

By Dr Adrian Morris

Oral Allergy Syndrome or Pollen-Food Allergy Syndrome is common amongst hay fever sufferers with certain stone fruits and vegetables causing an itchy mouthOral allergies occur in up to 40% of all Hay fever sufferers who are allergic to Silver Birch tree pollen. Once sensitised to the tree pollen, they progressively develop oral allergic symptoms when they eat certain fresh or raw fruit and vegetables.

Symptoms occur within a few minutes of oral contact and are almost always localised to the mouth and throat with lip and oral itching. Oral swelling with occasional glottic oedema may ensue but anaphylaxis is rare. Patients do not react to cooked fruit or vegetables as cooking reduces their allergenicity by damaging the protein structure. The Birch pollen-Apple Oral Allergy syndrome is the commonest pollen-food reaction seen in the UK.

Silver Birch tree pollen sensitivity (Birch Pollen Allergy)

Silver Birch pollen usually causes teenage sensitisation manifesting with hay fever symptoms in early Spring (February to April).  In their late teens and early 20’s they then develop troublesome localised oral itching and swelling when eating these fresh fruits, nuts and vegetables in the raw form – the “Oral Allergy Syndrome” or OAS.

Foods cross-reacting with Silver Birch Tree Pollen include:

FennelHoney (Pollen)Peanut

Other Food-Pollen Allergic Reactions

As mentioned above, the Birch pollen-Apple oral Allergy Syndrome is commonly seen in the UK. The major Birch Pollen PR10 pan-allergen Bet V 1 has a very similar structure to the major allergens in Apple, Hazelnut, Carrot, Cherry, Pear, Tomato, Celery, Potato and Peach. Hence we find Birch Pollen sensitised individuals have oral allergy to any one or combination of these fruits and vegetables.

Other pollen-food allergic syndromes include Grass pollen allergic rhinitics who have oral allergy to Melon, Orange. Tomato and wheat. Ragweed allergic people may react to Melon and Banana, While Mugwort allergic react to Apple, Carrot, Celery and Melon. People who are sensitised to natural latex in rubber gloves, catheters etc may react in a similar way to Avocado, Banana, Chestnut and Kiwi fruit and are at high risk to develop anaphylaxis when consuming these foods.

Other pollens causing food allergic cross-reactions:

Grass PollenMelon, Orange, Tomato, Watermelon, Wheat, Swiss chard.
Mugwort PollenApple, Carrot, Celery, Melon, Spices, Chamomile tea, Watermelon
Ragweed PollenBanana, Honey, Melon, Chamomile tea, Sunflower seeds

A certain amount of cross-reactivity occurs between foods of similar classes and this should be borne in mind if symptoms recur on specific food avoidance. For example if allergic to peanuts, then there is a high risk of being allergic to beans, peas, lentils, carob, senna and liquorice (all members of the legume family). But foods from divergent food families may cross react such as “celery-spice-carrot-mugwort syndrome”. This may be due to the presence of similar pan-allergens called Profilin and Lipid Transfer Protein (LTP) common to fruit, grass and vegetables and which accounts for the cross-reactivity we see between unrelated foods.  It would appear that allergic reactions to fruit and vegetables, which often coexist with pollen allergy, are on the increase. These pan-allergens seem to play a protective role in plants and are induced by environmental stress such as plant infections, soil conditions, changes in weather and storage conditions.   Birch pollen allergic people can have cross-reactions to apples and other fruit, grass pollen allergic people may react to melon, cereals and tomatoes, while those allergic to latex, react to avocado, chestnut, banana and kiwi-fruit. Profilin generally causes milder reactions and is destroyed by heat and cooking. Northern Europeans are more prone to mild oral allergic symptoms with their Silver Birch tree pollen allergies. However, Lipid transfer Protein (LTP) is heat and digestion resistant and can cause more severe systemic allergic reactions. Certain Peach allergic people sensitised to the LTP allergen Pru p3 are likely to have more severe allergic reactions.  People of southern European decent seem to be prone to more severe LTP fruit allergic reactions with anaphylaxis and no associated hay fever. There is now a blood test to measure Pru p3 specific IgE to help identify those at risk for fruit anaphylaxis.

Latex sensitivity

Some individuals who are allergic to Latex rubber may develop allergic symptoms on contact with certain foods.  Major Latex proteins have a similar structure to proteins found in fruit and nuts, the immune systems thus confuses these foods with Latex and a severe allergic reaction may occur.  Latex cross-reactive foods include:

Avocado, Banana,
Kiwi fruit, Litchi

Other foods may also cause allergic symptoms in latex-allergic patients include:

Passion FruitPineappleSpinachTomato

All patients with a history of Latex Allergy or Latex Anaphylaxis should be blood tested if food cross-reactions are suspected.  Latex Allergic people are most at risk for latex exposure in Hospital and at the Dentist.

Book a private appointment for Oral Allergy Syndrome

Written and researched by Dr Adrian Morris
Originally published  July 2012 and last reviewed 2nd January 2019.