The Oral Allergy Syndrome is the most common food-related allergy in adults. In actuality, this is not a direct food allergy, but rather represents cross-reactivity between distant remnants of tree or weed pollen still found in certain fruits and vegetables. Therefore, this phenomenon is only seen in tree and weed allergic patients, and is limited to ingestion of only uncooked fruits or vegetables. It is perhaps more aptly named the pollen-food syndrome.
The symptoms of oral allergy syndrome are classically itching and swelling of the lips, mouth, tongue, and throat within several minutes of ingestion of uncooked fruits and vegetables. The itchiness of the throat commonly results in the patient trying to relieve this symptom by rubbing the tongue against the soft palate making a characteristic “clucking” sound. Symptoms are almost always localized to the upper oral tract, but in limited instances, could involve generalized allergy symptoms. The vast majority of patients experience symptoms within five minutes of ingestion. Depending on the time of year, the presentation can be affected by the particular pollen season.
How Does This Occur
Symptoms result from digestion of fruit or vegetable proteins that cross-react with antibodies that also recognize tree or weed pollen proteins. It should be emphasized that this is not a direct allergy against a fruit or vegetable, though often this is the defining complaint that precipitates referral to an allergy specialist. Therefore, allergy testing is generally not necessary because it rarely yields a positive result as there is no sensitization that has occurred to the food itself, but only to the cross-reactive pollen.
Who is Affected
By definition, persons with oral allergy syndrome have allergy to either tree or weed pollen. Historically, this syndrome was first associated with birch tree pollen allergy, and subsequently with both mugwort and ragweed pollen allergy. We now recognize that it can occur in individuals allergic to any tree or any weed species. Several studies have examined the extent of this problem in tree or weed pollen allergic individuals, with estimates ranging from 25%-75% of such individuals reporting this phenomenon. While this is generally though of as an adult phenomenon, it is seen in children as well.
What Foods Are Responsible
Essentially, any raw fruit or vegetable can potentially elicit symptoms in tree or weed allergic individuals. However, this has been described most often with the following:
Birch pollen allergic patients have also been observed to have cross-reactivity to latex, grass, olive tree, and mugwort pollen.
Celery attributed symptoms are also seen in areas where birch is prevalent as well, as there is a high degree of cross reactivity.
It is also important to mention a related entity, the Latex-Fruit Syndrome, which operates under very similar circumstances. Latex is tree derived and its primary allergen shares similarities with fruit proteins. Latex is an omnipresent allergen in the environment, and there is high degree of contact in day to day activities.
The following food proteins have demonstrated cross reactivity with latex proteins:
The tried and true management strategy for a food allergy, no matter what the cause, is avoidance. However, most individuals do not have symptoms after ingesting cooked fruits and vegetables, as the heating process breaks down the allergenic proteins.
Many allergists recommended that individuals with oral allergy syndrome carry an EpiPen® or Twinject® device with them, to protect against throat symptoms, or the extremely rare case that may lead to anaphylaxis. Immunotherapy, or allergy shots, may seem like a logical and effective treatment, however several studies have not proven beneficial for oral allergy syndrome, though they are a well-established, highly effective treatment for pollen induced allergic rhinitis. Therefore, allergy shots are not offered as a specific treatment, although many patients on allergy shots for allergic rhinitis may see some improvement in oral allergy syndrome symptoms.