Oral Allergy syndrome


Oral Allergy Syndrome(OAS) also known as Pollen Food Syndrome (PFS) usually occurs in people who are allergic to pollen from trees, grasses or weeds. It can also be defined as a type of food allergy classified by cluster of allergic reaction in the mouth in response to eating certain fruits, nuts and vegetables that typically develop in adult’s hay fever sufferers.Before understanding the meaning of Oral Allergy Syndrome,let’s know what is Hay fever?

Hay fever also known as allergic rhinitis is caused by allergic response to airborne substances such as pollen. The susceptible person shows same signs and symptoms like cold such as sneezing, congestion,runny nose and sinus problem but it is different from cold as the causative agent for cold is virus and not pollens.

Studies have shown that pollens from trees, grasses and weeds contain protein of similar structure to those present in different fruits, vegetables, nuts and spices. These proteins which play important role in plant growth and provide defence against disease, are recognized by the immune system of hay fever sufferer and can trigger allergic reaction in asusceptible person. Therefore this condition mainly affect in people who get spring and summer time hay fever.

Symptoms of Oral Allergy Syndrome (OAS)

-itching or burning sensation in the lips, mouth or ear canal.

- swelling of lips and tongue, throat and other parts ofbody

-sensation of tightness in the throat

-wheezing, nasal congestion or difficulty in breathing

-vomiting, diarrhoea

-severe indigestion and stomach cramps

-dizziness and fainting

Mechanism of Oral Allery Syndrome (OAS)

In this syndrome, immune system produces antibodies that are capable of binding both pollen proteins and structurally similar food proteins.The same immune system response can trigger allergy system in two different situations: hay fever (in response to pollen) and food allergy (in the presence of food). This is the example of cross reactivity. The triggering molecule involved is called allergen. E.g. of allergens are

Birch pollen –apple, almond, carrot, hazelnut, kiwi, peach,pear, and plum.

Grass pollen –celery, melons, oranges, peaches, and tomato.

Ragweed pollen –banana, cucumber, melons, sunflower seeds

The immune system triggers cells to release antibodies Ig E to neutralize the antigen. Ig E antibodies sense the antigen and signal the immune system to produce chemical called histamine in blood. These chemicals in turn causes a range of allergy signs and signals such as nausea, vomiting,dizziness, swelling etc.

People affected by oral allergy syndrome can usually eat same fruits or vegetables in cooked form because the proteins are distorted during the heating process, so that the immune system no longer recognizes the protein.


You should see a doctor or allergist if you have foodallergy symptoms shortly after eating food. Doctor will go through your family history and as well as your diet plan. The best way of treatment is the avoidance of food that triggers the reactions. Secondly if you get allergy from uncooked food, try to avoid them as well. A skin prick test can be done to determine your reaction to the particular food. Antihistamines and epinephrine can be recommended by doctor to provide relief. In case of food avoidance it is necessary to see your dietician also to make sure you have balanced diet if you eliminate the trigger food.




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