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Oral allergy syndrome

Oral Allergy Syndrome or OAS is an allergic reaction to certain (usually fresh) fruits, nuts, and vegetables. The allergy is not actually an allergy to food but a syndrome that develops in hay fever sufferers. The immune system mistakes the food proteins for the pollen proteins and causes an allergic reaction. Another term used for this syndrome is "Pollen-Food Allergy."



OAS sufferers may have a number of reactions that usually occur very rapidly, within minutes of eating a trigger food. The most common reaction is an itching or burning sensation in the lips, mouth, and/or pharynx. Sometimes other reactions can be triggered in the eyes, nose, and skin. The most severe reactions can result in asthma problems or anaphylaxis.[1] If a sufferer is able to swallow the food, there is a good chance that there will be a reaction later in the gastrointestinal tract. Vomiting, diarrhea, severe indigestion, or cramps may occur.[2]

Cross reactions

Allergies to a certain pollen are associated with OAS reactions to certain foods. For instance, an allergy to ragweed is associated with OAS reactions to banana, watermelon, cantaloupe, honeydew, zucchini, and cucumber. This does not mean that all sufferers of an allergy to ragweed will experience adverse effects from all or even any of these foods. Reactions may begin with one type of food and with reactions to others developing later. However, it should be noted that reaction to one or more foods in any given category does not necessarily mean a person is allergic to all foods in that group. Often well-cooked, canned, or frozen food offenders cause no reaction due to denaturation of the cross-reacting proteins.[1]

Allergy trigger Cross reactors
Alder pollen
  • almonds
  • apples
  • celery
  • cherries
  • hazel nuts
  • peaches
  • pears
  • parsley
Birch pollen
  • almonds
  • apples
  • apricots
  • carrots
  • celery
  • cherries
  • coriander
  • fennel
  • kiwi
  • nectarines
  • parsley
  • parsnips
  • peaches
  • pears
  • peppers
  • plums
  • potatoes
  • prunes
  • soy
  • wheat
  • Potential: hazel nuts, and walnuts
Grass pollen
  • melons
  • tomatoes
  • oranges
Mugwort pollen
  • carrots
  • celery
  • coriander
  • fennel
  • parsley
  • peppers
  • sunflower
Ragweed pollen
  • banana
  • cantaloupe
  • cucumber
  • honey dew
  • watermelon
  • zucchini
  • Potential: Dandelions or chamomile tea


An OAS sufferer should avoid foods to which they are allergic. Peeling or cooking the foods has shown to reduce the effects of the allergy in the throat and mouth, but may not relieve reactions in the gastrointestinal tract. Antihistamines may also relieve the symptoms of the allergy. Persons with severe reactions may consider carrying injectable medication (such as an EpiPen) to relieve themselves if necessary. Allergy immunotherapy has improved or cured OAS in many patients.

Finally, a person may choose to eat substitute foods, such as the following:

Substitute Raw Fruits

Berries* (strawberry, blueberry, raspberries, etc.), citrus* (orange, mandarins, etc.), grapes, currants, gooseberries, guava, mango*, figs*, pineapple*, papaya, avocado, persimmon, pomegranates*, watermelon*.

Substitute Raw Vegetables

Mustard family (cabbage, cauliflower, broccoli, watercress, radish)
Goosefoot family (spinach, Swiss chard)
Composite family (green onions)

Substitute Nuts

Peanut*, cashew, pistachio, Brazil, macadamia, pine nut.

* May cause a cross-reaction with OAS.


  1. ^ a b Tidwell, Judy "Oral Allergy Syndrome" (accessed July 5, 2006)
  2. ^ (accessed 38 July, 2006)


  • OAS information from the Canadian Food Inspection Agency
  • OAS at
  • Dr. Anthony Ham Pong, Oral Allergy Syndrome -- published in June 2000 AAIA (Allergy/Asthma Information Association) newsletter. Accessed January 5, 2007.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Oral_allergy_syndrome". A list of authors is available in Wikipedia.
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