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The Allergenic March - Common Allergies
Oral Allergy Syndrome
Oral Allergy Syndrome is the medical term for an allergic reaction to food which is limited to the lips, mouth and throat.
These symptoms usually start within minutes of eating and settle down within an hour. Sometimes these symptoms can occur at the start of a more severe reaction. This would not then be classified as oral allergy syndrome. Oral allergy syndrome is not a serious problem unless swelling in the mouth or throat is sufficient to affect breathing. Fortunately, this is very unusual.
What causes oral allergy syndrome?
Fresh fruit, vegetables and nuts are common causes of oral allergy syndrome. Some patients are allergic to a wide range of these foods. There are well-recognised groups of these foods which can cause symptoms.
The key to oral allergy syndrome is the association of groups of food allergies with seasonal allergic rhinitis or `hayfever`. It has been shown that pollens from trees (especially Birch), grasses and weeds contain proteins of similar structure to those present in certain fruit, vegetables, nuts and spices. These proteins are recognised by the immune system of a person with hayfever and can trigger an allergic reaction in a susceptible person when they eat a food which shares the same protein as the pollen. The most well-recognised cross-reactions occur with allergy to tree pollens, and are shown in the table below.
The associations with grass pollen are less clear cut and a specific "syndrome" has not been described. It is important to recognise that some people have more serious fruit, vegetable and nut reactions, which do not fall into the oral allergy group. When tropical fruits are a trigger, latex sensitivity may be the underlying cause.
What can be done for oral allergy syndrome?
If you have oral allergy symptoms, it is important that you are referred to an allergy specialist. This will ensure that you have a correct diagnosis and appropriate treatment. The specialist will take details of your reactions to decide whether there is evidence of more serious allergy and will advise if you should carry adrenaline. This is particularly important for those with nut reactions. Allergy skin prick tests or a blood test will usually be needed.
Avoidance of the foods that cause your reactions is most important. Your allergy specialist will be able to help you find out which group of foods should be avoided. Usually, cooking will destroy the allergens so that you need not worry about cooked food. There are some exceptions to this. If you react to celery or nuts then it may be safest to avoid these even if cooked. If you have had serious reactions such as breathing difficulties or shock, you should avoid the foods in any form. Immunotherapy ("Desensitisation") with the relevant pollen extract has been tried but is not particularly effective. It is only indicated for treatment of severe hayfever symptoms.
If you have a reaction, keep calm, rinse your mouth with some plain water and rest. The tingling, itching and swelling should settle within 30 minutes to an hour. Take a dose of an antihistamine.
If you have difficulties with breathing, your voice becomes hoarse, your throat is closing up or you feel faint, you may need additional treatment and you should call an ambulance immediately. If you have an adrenaline injector you should administer a dose but still call for an ambulance. A dose of antihistamine may be taken if you are able to swallow. Fortunately, these symptoms are uncommon.
In a few people, preparation of food for your familymay cause reactions. Wearing gloves or a mask can help by preventing contact with allergens. Reactions include sneezing attacks (when peeling or scraping fruit & vegetables, particles can get into the air), conjunctivitis (if you touch your eye after touching the fruit or vegetable) and weals on your hands (if there is broken skin, allergens can penetrate). Avoid latex rubber gloves as these can cause allergic reactions.
Recognised associations between pollen and food allergies
Tree Pollens (most common reactions are in bold)
Grass Pollens (most common reactions are in bold)
Weed Pollens (most common reactions are in bold)