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Oral Allergy Syndrome (OAS)

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What is Oral Allergy Syndrome?

Also known as pollen fruit syndrome or pollen fruit allergy syndrome (PFAS), oral allergy syndrome is a cross-reactivity that occurs in patients with existing allergic rhinitis when they consume certain fruits and vegetables.

Since the proteins found in these fruits and vegetables are very like the ones found in certain pollens, patients with pollen-triggered rhinitis have a contact allergic reaction when eating these foods. As an example, as many as three out of four adults with an allergy to birch tree pollen will have a contact allergic reaction when consuming apples or celery.

The symptoms associated with OAS often appear as soon as the patient has eaten the fruit, affecting the face, mouth, lips, tongue, and throat. OAS is considered a mild allergy, but on rare occasions it can cause more serious reactions.

Unlike pollen allergies, OAS can occur at any time of year, given the fact that many fruits and vegetables are sold out of season in the modern world. While there is currently no definitive test for identifying the presence of OAS, patients with symptoms related to the disorder often have a positive diagnosis of a pollen allergy and have experienced regular symptoms when consuming certain fruits and vegetables.

Common Triggers of Oral Allergy Syndrome

Patients with OAS can be triggered by a single food source or from many different types of food. In some cases, patients will also only react to certain varieties; for example, someone might react to one type of red apple, but not to a type of green apple.

In general, a patient’s triggers correlate with whatever type of seasonal allergy they have.

  • Those with ragweed allergies react to: Bananas, melons, zucchini, cucumber, dandelions, and chamomile
  • Those with birch allergies react to: apples, peaches, pears, cherries, apricots, plums, prunes, nectarines, kiwi, carrots, celery, potatoes, peppers, coriander, hazelnuts, and more
  • Those with grass allergies react to: peaches, celery, tomatoes, oranges, and melons
  • Those with mugwort allergies react to: apples, celery, kiwi, peanuts, fennel, carrots, parsley, sunflower seeds, peppers, and coriander
  • Those with alder allergies react to: pears, apples, celery, almonds, hazelnuts, cherries, peaches, and parsley
  • Finally, those with a latex allergy may react to: avocados, kiwis, bananas, chestnuts, and papaya.
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Signs and Symptoms of Oral Allergy Syndrome

The signs and symptoms associated with oral allergy syndrome vary from one patient to the next. In general, the most common symptoms include:

  • Itchiness in the face and in the mouth
  • Swelling in the mouth, face, lips, tongue, and throat

Most oral allergy syndrome symptoms appear right after someone has consumed raw vegetables or fruits, but occasionally a patient will experience a delayed reaction and have symptoms hours later. Additional, less common symptoms can include irritation in the gums, eyes or nasal cavity. While symptoms of oral allergy syndrome can happen all year round due to the wide availability of out of season fruits and vegetables, symptoms are also worse during the spring and fall months when there is more pollen in the air.

Risk Factors for Oral Allergy Syndrome

The main risk factor for oral allergy syndrome is the presence of a pre-existing pollen or latex allergy. Research has shown that patients with OAS may have some additional risk factors beyond atopy, though research in this area is ongoing. It is known that cases of OAS appear more frequently in women than in men.

How Oral Allergy Syndrome is Diagnosed

As with diagnosing any condition, diagnosing oral allergy syndrome involves multiple steps. Diagnosing the condition can be challenging given the multiple factors involved. A doctor will likely begin with a physical exam and medical history.

When taking the medical history, the doctor will ask after a family history of allergies as well as if the patient has any diagnosed allergies. A doctor or allergist may also recommend testing. Testing options for oral allergy syndrome can include both skin tests and blood tests to confirm a diagnosis. The presence of a confirmed test for a pollen allergy can, of course, help in the diagnostic process.

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Oral Allergy Syndrome Treatment Options

As with all allergies, the best way to treat oral allergy syndrome is to avoid exposure to the foods or vegetables associated with a patient’s particular diagnosis. Oral allergy syndrome treatment can also include OTC and prescribed antihistamines or immunotherapy. There are also some natural remedies when it comes to how to treat oral allergy syndrome. Oral allergy syndrome natural treatment options include peeling a fruit to avoid concentrated proteins, cooking fruits and vegetables, and eating canned fruits and vegetables during spring and fall.

Oral Allergy Syndrome FAQ

Is Oral Allergy Syndrome Curable?

There is no known cure for any allergy, including oral allergy syndrome. There are many ways in which patients can manage the condition and eliminate many if not all symptoms. The best way to avoid an episode of OAS is to avoid the triggering fruit or vegetable. Antihistamines can also help assuage symptoms.

Is Oral Allergy Syndrome Dangerous?

By and large, oral allergy syndrome produces a very mild allergic reaction. In very rare cases, oral allergy syndrome can lead to serious reactions such as anaphylaxis. When patients are in anaphylactic shock, they become disoriented, have trouble breathing and require immediate medical attention.

Can Oral Allergy Syndrome Cause Hives?

Oral allergy syndrome can cause itchiness and rashes. It also sometimes leads to hives, especially around the mouth and face. These reactions typically do not progress beyond this localized region. Symptoms are also generally short in duration and abate once the food has been ingested or is no longer being consumed.

How Long Does Oral Allergy Syndrome Last?

Oral allergy syndrome typically leads to a short, acute manifestation of symptoms. Generally speaking, any reactions triggered by oral allergy syndrome disappear after the triggering fruit is no longer near the patient. It is extremely rare for symptoms of OAS to last very long or cause serious harm.

How Common Is Oral Allergy Syndrome?

Oral allergy syndrome is quite common. It is estimated that as many as 75 percent of people with pollen allergies have an associated oral allergy syndrome. Anyone with a diagnosed allergy to pollen who has experienced some discomfort when consuming certain fruits or vegetables should consider contacting a doctor or allergist to confirm whether or not they have OAS.