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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.

Contents 1 Symptoms 2 Cross reactions 3 Treatment 4 Notes 5 References

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]

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. 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 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" About.com (accessed July 5, 2006)
2. ^ http://www.calgaryallergy.ca/Articles/English/Oral_Food_Allergy.htm ( accessed 38 July, 2006)

• OAS information from the Canadian Food Inspection Agency
• OAS at About.com
• Dr. Anthony Ham Pong, Oral Allergy Syndrome -- published in June 2000 AAIA (Allergy/Asthma Information Association) newsletter. Accessed Jan 5, 2007.