Tree Pollen Allergy And Foods: The Oral Allergy Syndrome

April 9, 2010

Certain fruits, vegetables and nuts contain allergens that cross react with tree pollen, specifically the pollen of birch and alder.  These foods include the following:

Nuts: Almond, Hazelnut

Fruit: Apple, Apricot, Cherry, Kiwi, Nectarine, Peach, Pear, Persimmon, Plum, Orange

Vegetables: Carrot, Celery, Fennel, Potato

Although most people with tree pollen allergy can eat these foods without any problem, up to 1/3 of people who are allergic to tree pollen will develop symptoms of what is called the Oral Allergy Syndrome.  The most common of these symptoms is itchiness of the mouth and throat.  A small minority of people who have symptoms of the Oral Allergy Syndrome will have more widespread symptoms seen in other forms of food allergy and it is sometimes difficult to differentiate those who will have just the oral and perioral symptoms from those who have more general allergy symptoms.   Most people with the Oral Allergy Syndrome are only allergic to a few of the foods listed above and not all of them.  In my experience the most common foods to cause symptoms are apples, carrots, cherries and peaches.   Having said that, I do have patients who react to all of the foods.

It is very important to point out that the tree pollen cross reacting allergens in these fruits and vegetables are generally not the major allergens of the foods, but are minor allergens that tend to be heat labile.  That means that these minor allergens lose their effect as allergens with exposure to heat and usually people with this form of food allergy can eat the food in a cooked form without any problem.  So raw apples are a problem, but apple pie, apple sauce and apple juice are usually OK.  It is not unusual for me to see a patient in my office who thinks they are allergic to the skin of the apple or to a pesticide sprayed on the apple because they know they are fine with cooked apple.   Invariably these are people with tree pollen allergy and they are experiencing the Oral Allergy Syndrome.  Also, these allergens tend to be acid labile which means that they lose their effect as allergens when they are exposed to stomach acid.  That is one reason why the symptoms are usually confined to the mouth.

There is some evidence that the common nasal and eye allergy symptoms that people with tree pollen allergy have, may get worse with exposure to these foods in people with the Oral Allergy Syndrome.  I usually recommend that people who have oral itchiness with exposure to one or more of these foods avoid those foods completely in the raw form, especially during the pollen season as it can make their other pollen allergy symptoms worse.

It is important to speak to your allergist about this form of food allergy in order to determine if you need to avoid the foods completely or only in the raw form.  Remember a small percentage of people with this form of food allergy can have more widespread symptoms of an allergic reaction or anaphylaxis with exposure.

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