Mother always told you to eat your fruits and vegetables. Sometimes, mother was wrong.
A less severe form of food allergy, called oral allergy syndrome, is a reaction to proteins in common raw fruits, vegetables, nuts and seeds. It’s called “oral allergy” syndrome or OAS because its symptoms are usually limited to the lips, mouth, tongue and throat.
Estimated to affect about one-third of pollen allergy sufferers, oral allergy sydrome (sometimes called pollen allergy syndrome) is more widespread than the higher profile – and more dangerous – allergies to peanuts, dairy and eggs.
If you have oral allergy syndrome, chances are that you also have allergies to pollen from trees such as birch and alder, and/or to pollens from ragweed and grass.
Think of it as an allergy by association – or a cross-reaction  – because your immune system, already primed to attack tree, plant and grass pollens, does not recognize the subtle differences between their proteins and those contained in foods as basic as an apple.
Not Usually Life-Threatening
One reason for oral allergy syndrome’s lower profile is that, unlike other food allergies, its symptoms are not usually life-threatening. Another is that it is relatively easy to avoid.
“You may eat something that contains traces of peanut, dairy or egg, but you aren’t going to unknowingly bite into a raw apple,” notes Dr. Antony Ham Pong, an allergist and based in Ottawa.
High Incidence of Oral Allergy Syndrome
About 10 per cent of the population, or roughly one-third of North Americans with pollen-related allergies, are thought to be affected by OAS.
Ham Pong says he usually first sees patients when they’re between 8 to 10 years old. It’s not clear, however, why no more than one-third of hay fever sufferers are affected.
Oral Allergy Syndrome Serious for Some
While usually a mild form of allergy, 1 to 2 per cent of those with oral allergy syndrome are susceptible to severe (anaphylactic) reactions. This is more often the case when the offending foods include nuts or peanuts. (Consult an allergist if you react to peanuts or nuts of any kind.)
What Foods are Linked to Oral Allergy Syndrome?
The list is long and made up of common, healthy fare that in a perfect world would be part of a balanced diet. The foods associated with birch or alder pollen allergies, for instance, include apples, pears, peaches and tomatoes, as well as vegetables like carrots, celery, potatoes, and peas.
If some of those bother you, cumin or coriander may as well. The tree pollen list goes on to include: hazelnuts, soybeans and sunflower seeds. (Though not everyone with tree pollen-related food allergies will react to all foods on these lists.)
Peanuts may cause a reaction but this is not the same as someone who has a serious peanut allergy, whose life may be at risk if he accidentally ingests a trace of them. That said, if you have even a mild oral allergy syndrome reaction to any kind of nut, Ham Tong counsels that it’s best to stop eating them altogether because of their allergenic properties. Better safe than sorry!
The allergist says foods that may trigger a more extreme oral allergy syndrome reaction include celery, kiwi, hazelnuts, peaches, apricots and apples. And speaking of apples, Granny Smith and Golden Delicious have proven to be more allergenic than other varieties.
Ragweed allergies have been linked to oral allergy syndrome reactions to bananas, melons, zucchini and cucumbers, while those who are allergic to grass pollens  may find themselves sensitive to produce like oranges, kiwis and tomatoes.