Oral Allergy Syndrome

Oral Allergy Syndrome

Oral allergy syndrome (OAS), also known as pollen-food allergy syndrome (PFAS), is a form of food allergy triggered by fruits, vegetables, and nuts. It normally causes mild allergic reactions confined to the mouth, lips, and throat. This condition arises due to a cross-reaction with plant pollens, such as those from trees, grasses, or weeds.

Who is likely to be affected by OAS?

OAS is primarily common among people allergic to grass, trees, and weed pollen, which are often linked to seasonal allergies or allergic rhinitis. Kids below the age of three are rarely affected by this condition since it takes several years of exposure to pollen to trigger such allergies.

How common is OAS?

Although the precise number of people diagnosed with oral allergy syndrome is unknown, it is the most prevalent food allergy among grownups. According to studies, OAS is thought to affect 47% to 70% of those with pollen allergies.

Is OAS a serious condition?

In most cases, oral allergy syndrome is not dangerous. Many people only experience mild swelling or itching because of their allergic reaction. Anaphylaxis is a serious allergic reaction that affects no more than 2% of individuals with OAS. This condition can be fatal and causes breathing difficulties.

How does OAS affect the body?

OAS occurs when the immune system mistakenly identifies some foods (trigger foods) as harmful substances. This immune response causes itching or swelling in the lips and mouth. Normally, stomach acid neutralizes the proteins responsible, preventing the reaction from progressing beyond the mouth.

Symptoms and Causes

Oral allergy syndrome symptoms often develop shortly after consuming trigger foods. They can include:

  • Itching, tingling, or mild swelling of the lips, tongue, mouth, or throat.
  • Bumps on the lips or inside the mouth.

Other less common symptoms that can affect other body parts are:

  • Hives or rashes.
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  • Itchiness, redness, or swelling of the skin after touching certain raw foods.
  • Severe reactions like trouble breathing (anaphylaxis) are extremely rare.

Foods Likely To Cause OAS

OAS is caused by proteins in certain vegetables, fruits, and nuts that mimic the structure of pollen proteins. This triggers an immune response that is like a pollen allergy. The specific foods that cause OAS vary depending on your other allergies.

It’s comparable to a puzzle piece that appears to fit, even though it doesn’t. While some individuals react to foods linked to their pollen allergies, others may experience food reactions without a corresponding pollen allergy.

List of OAS foods

The likelihood of reacting to specific foods depends on the type of pollen allergy:

Birch tree pollen:

  • Herbs: Coriander, aniseed, caraway, fennel, parsley.
  • Legumes: Peanuts, soybeans.
  • Seed Fruits: Apples, avocados, kiwis, pears.
  • Stone Fruits: Apricots, peaches, cherries, plums.
  • Tree Nuts: Almonds, hazelnuts.
  • Vegetables: Carrots, celery.

Grass pollen:

  • Oranges
  • Melons
  • Potatoes
  • Tomatoes
  • Swiss chard

Ragweed Pollen:

  • Bananas
  • Artichokes
  • Cucumbers
  • Zucchini
  • Melons

Mugwort pollen

  • Garlic
  • Mustard
  • Peppers
  • Herbs: Caraway, aniseed, coriander, fennel, parsley
  • Vegetables: Cabbage, cauliflower, carrot, celery, parsnip, broccoli, onion

Additional foods associated with oral allergies are berries, figs, citrus fruits, grapes, pineapples, mangoes, and pomegranates.

Diagnosis and Tests

Oral allergy syndrome is diagnosed by a medical professional (mostly an allergist) based on your symptoms.

An allergist may use the following tests to confirm OAS:

  • Allergy skin test: The provider uses a small applicator to lightly scratch your skin with a tiny amount of an allergen, such as tree pollen or suspected trigger foods. If a hive develops at the test site, it indicates an allergic reaction.
  • Food challenge test: This involves consuming increasing amounts of a specific food under medical supervision while monitoring for allergic reactions.

Management and Treatment

OAS does not have a specific cure. Once you cease consuming the trigger food, any reactions you may have should fade away on their own in approximately half an hour. An antihistamine can help manage symptoms, though mild reactions often subside faster than the medication takes effect.

OAS medications options

  • Antihistamines: These medications obstruct chemicals that trigger mild allergic reactions. Over-the-counter options include fexofenadine (Allegra®), diphenhydramine (Benadryl®), and loratadine (Claritin®). You may need to try different types to find the one that is effective.
  • Epinephrine: This is used in cases of severe allergic reactions (anaphylaxis). Injecting epinephrine (such as Auvi-Q® and EpiPen®) eases swelling and opens air paths, making breathing easier. Your allergist may recommend epinephrine if you’ve previously experienced severe reactions.

What to eat if you have OAS

People with OAS can usually consume most foods without issues. Reactions are often limited to specific vegetables, fruits, or nuts.

Prevention

Avoiding foods that trigger reactions is the only way to prevent oral allergy syndrome. You may also be able to minimize or avoid a reaction by considering these measures:

  • Cooking your trigger foods: When fruits and vegetables are heated, the protein is altered, hence preventing reactions. Typically, cooked sauces, foods, and pasteurized juices are safe for people with OAS.
  • Refraining from certain foods during peak allergy seasons: For most people, spring, summer, or fall are the worst seasons for seasonal allergies. When you have seasonal allergies, your reaction may be adverse to trigger foods.
  • Proactively treating your allergies: Some people may be able to prevent reactions to trigger foods by taking allergy medications on a daily basis.
  • Getting allergy shots (immunotherapy): Gradually increasing doses of allergens through allergy shots can help your body build tolerance. As a result, it may help reduce or eliminate reactions to certain foods.

Outlook / Prognosis

What to expect if you have oral allergy syndrome

Severe allergic reactions are uncommon in cases of oral allergy syndrome. You should consider avoiding a particular food if the symptoms it causes concern you.

Does OAS resolve on its own?

For some, OAS can disappear even though there is no known cure. Your body can adapt to foods that previously caused reactions, allowing you to tolerate them in the future.

Conclusion

While most people find oral allergy syndrome annoying, some experience severe side effects. If you are concerned about food allergies, consult an allergist or healthcare professional. You could still enjoy your favourite foods or find suitable alternatives that won’t cause discomfort.

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