ORAL ALLERGY SYNDROME

fruit stand
Birch trees and grass
watermelon slices
gourds

What is OAS?

Oral Allergy Syndrome, or OAS, is an allergic reaction that is triggered when you eat certain raw fruits, vegetables, seeds, spices, and/or nuts. It is caused by a cross reactivity between food proteins and pollens and occurs in nearly 70 percent of pollen-allergic people. The allergic reaction usually happens in concurrence with hay fever or high pollen seasons in spring or late summer/early fall. Often the food proteins can be destroyed by baking, cooking or processing the food; however, celery and nuts are known exceptions.


Symptoms that may occur while eating the food include an itching, burning, and/or tingling sensation in your mouth and throat. You may also experience:


  • swelling in your lips, tongue, and throat
  • watery, itchy eyes
  • runny nose
  • sneezing


Even handling the food can sometimes cause the above reactions as well as a skin rash. Symptoms usually last for a few seconds to a few minutes and rarely worsen. Studies have shown that more severe symptoms, such as vomiting, cramps, diarrhea, and difficulty breathing, can happen in up to 9 percent of people with OAS, and up to 2 percent may experience anaphylaxis.


Continue reading for information on which pollens trigger OAS in certain foods. You can also view a detailed chart from the American Academy of Allergy, Asthma & Immunology here.


Spring Pollen:

The following tree and grass pollens occur in the spring and early summer seasons. Their cross-reactive foods are listed below.


Alder Pollen: almonds, apples, celery, cherries, hazelnuts, peaches, pears, parsley


Birch Pollen: almonds, apples, apricots, avocados, bananas, beans, carrots, celery, cherries, chicory, coriander, fennel, fig, hazelnuts, kiwi, nectarine, parsley, parsnips, peas, peaches, pears, peppers, plums, potatoes, prunes, soybean, strawberries, walnut, wheat, potential peanuts


Summer Pollen:

The joys of a summer harvest often include juicy tomatoes, fuzzy peaches, and other tempting fruits, but these fruits and some vegetables can prompt OAS as they're cross-reactive with certain prolific summer grasses.


Timothy & Orchard Grass Pollen: fig, melons, oranges, peach, white potatoes, tomatoes, watermelon


Fall Pollen:

Mugwort and ragweed are known fall allergens, with ragweed causing troublesome hay-fever symptoms for a majority of allergy sufferers. In especially high pollen seasons, you may experience cross reactivity with the following associated foods:


Mugwort Pollen (celery-mugwort-spice syndrome): aniseed, caraway, carrots, celery, coriander, peppers, fennel, parsley, sunflower


Ragweed Pollen: banana, cantaloupe, honeydew, watermelon, white potatoes, cucumber, zucchini, Echinacea, artichoke, dandelions, hibiscus or chamomile tea

OAS reactions may begin with one type of food and develop with others later, but it's important to note that a reaction to one or more foods in any category does not necessarily mean you're allergic to all foods in that group. Some people may experience OAS with only one food, while others may have an allergic response to many. Keeping a food journal of any reactions you may experience will help you and your allergist narrow down your triggers.


Some foods can have cross reactivity with any of the pollens mentioned above. These are: berries (strawberries, blueberries, raspberries, etc.), citrus (oranges, lemons, etc.), grapes, mangos, figs, peanuts, pineapples, pomegranates, and watermelon.


In the Raw:

Allergic reactions to any of these foods typically occur when they're eaten raw. If you experience OAS to certain raw foods, you may be fine eating them cooked, canned, microwaved, baked, or even frozen. The only exceptions can be celery and nuts. While a reaction can show up anytime during the year, you may find that your OAS occurs only during an especially high pollen season, especially if your hay fever or seasonal allergic reactions are significant.


Testing for OAS:

Testing for Oral Allergy Syndrome can be confusing. Some brands of fruit may cause worse reactions than others, and the ripeness of the fruit can also vary your reaction. It may be that removing the peel from some foods, such as apples, removes your trigger. Testing with fresh foods is therefore more reliable than using an extract, which is commonly used during standard skin testing.


Managing OAS:

An accurate diagnosis of your allergens should include a history of your symptoms as well as an elimination diet of potentially triggering foods. A skin test and/or allergy blood test can be used to potentially identify not only food allergens but also the corresponding pollen triggers.


Helpful Tips:

Here are some ways to limit your exposure to foods that may trigger oral allergic symptoms:

  • Cook or process foods you believe are triggers for an allergic reaction.
  • If you sense an allergic reaction starting, stop eating the food right away, and, if you're worried about your symptoms, take an antihistamine. Severe reactions may develop if you keep eating!
  • If you have a severe reaction, use epinephrine and visit the closest emergency room or walk-in clinic.
  • Allergy shots for seasonal pollens causing your OAS may help! Talk with your board-certified allergist.


Need this information for on the go? Download a printable copy here.

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References:

Oral allergy syndrome–pollens and cross-reacting foods. American Academy of Allergy, Asthma & Immunology Media Library.

Oral Allergy Syndrome (OAS). Nguyen, Jenna T., MD. Tourangeau, Louanne M., MD. Walford, Hannah H, MD. Stanford Health Care, Allergy, Asthma & Immunology. Menlo Park, CA.

Oral Allergy Syndrome. Pong, Anthony Ham, MD. Allergy Asthma Information Association. Ottawa, Ontario.

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