Oral allergy syndrome

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Oral allergy syndrome or OAS is an allergic reaction to certain (usually fresh) fruits, nuts, and vegetables that develops in hay fever sufferers.^[1] OAS is a food allergy: the immune system mistakes the food proteins for pollen proteins and causes an allergic reaction to the food. Another term used for this syndrome is '"Pollen-Food Allergy."'

It is treated like any other allergy, with medications and avoidance of anything that triggers a reaction.

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

[edit] Symptoms

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. Swelling of the lips, tongue, and uvula and a sensation of tightness in the throat may be observed. Seldom it can result in anaphylaxis.^[2] If a sufferer swallows 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.^[3]

[edit] Treatment

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.

[edit] Mechanism

In OAS, the immune system produces antibodies that are capable of binding to both pollen proteins and certain highly similar food proteins. Consequently, the same immune system response can trigger allergy symptoms in two different situations: hay fever (in the presence of pollen) and food allergy (in the presence of certain foods).

The antibody may react to the linear (amino acid) sequence of the protein or to a conformational epitope. If the response is to the conformational epitope, then the person with OAS may be able to eat the food when it is cooked, but not when it is raw. If the response is to the linear sequence (common in tree pollen/nut allergies), then cooking the food has no effect on its ability to trigger an allergic reaction.

[edit] 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, pasteurized or frozen food offenders cause no reaction due to denaturation of the cross-reacting proteins.^[2]

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 kiwifruit 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
Possible Cross-Reactions (to any of the above)	berries (strawberries, blueberries, raspberries, etc) citrus (oranges, lemons, etc) grapes mango figs peanut pineapple pomegranates watermelon

[edit] Notes