Food Allergy Diagnosis

Food allergy is an unfavorable immune response to a food protein. Sometimes the food consumed by a person is wrongly identified as harmful by the immune system and that is referred to as allergy.

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Food causing allergy are of various types such as gluten, herbs, spices, crustaceans, vegetables, milk, egg, tree nuts, peanuts, soybeans, fish and so on. Allergic reactions caused by vegetables may lead to itching of lips, throat or mouth, which is commonly known as Oral Allergy Syndrome. Tree nuts such as hazelnuts and walnuts can also lead to Oral Allergy Syndrome.

Some people are allergic to fruits that contain pollen. So, it is advisable for such people to use cooked fruits. Some people can also have allergic reactions to fruits such as avocado, banana and kiwi.

There are certain ingredients like aniseed, garlic, chamomile and sesame used to enhance the flavor of the food. These substances might contain allergens that lead to severe reactions in the body.

Crustaceans such as lobsters, crabs, shrimps and mollusks such as oysters and snails can lead to life threatening reactions. The flesh proteins in fish lead to allergic reactions. Milk protein and egg white are the common allergens in children.

Similarly, beans, peas and lentils can lead to food allergy. Peanuts can lead to severe or fatal reactions. The raw and cooked legumes can also lead to allergic reactions. So, different food products can cause food allergy and diagnosis is very important if food allergy occurs.

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Doctors should examine the patient thoroughly and find out if there is a severe reaction to a particular food product.

One of the most important tools in diagnosis is the patient’s history. It is necessary to know about the patient’s food habits. Diagnosis involves skin tests, blood tests and some food challenges.

The doctors would like to know when the reaction happened exactly after the time of food intake.

It is also important to know if the reaction is due to a particular food.

Then, the next step is to know whether everyone who ate the food is affected or only one person is allergic to that food. The amount of food intake by the patient is also very useful information during diagnosis. The next thing to know is whether the food was cooked properly or whether the food was little raw or overcooked. History alone is not sufficient during diagnosis.

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The doctor might ask the patient to check whether the same food causes allergic reaction again.

The next step would be the elimination of a particular diet. Sometimes the doctor might ask the patient to avoid having a particular food product. Later, if there is no symptom of allergic reaction, then the doctor can proceed with the diagnosis. After a short period of time, when the doctor directs the patient to consume the same food again and if the symptoms return, then the doctor can easily come to a conclusion. This kind of diagnosis is not suitable when the allergic reactions are life threatening.

Skin Test :

In some cases, scratch-the-skin test is performed. The test is indicated positive if the patient has IgE antibody specific for the food being tested on the skin’s mast cells.

This is a quick, simple and safe test.

Blood Test :

Blood tests cost more than skin tests. Doctors make use of blood tests such as RAST and ELISA. Using these tests, the food-specific IgE antibodies are measured in the blood of the patients.

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Food Challenge :

Apart from these tests, the other way of diagnosis is double-blind food challenge. Samples of suspected food products that lead to allergic reactions are placed in opaque capsules.

The patient and the doctor are blindfolded. They are not aware about which capsules contain the suspected foods. After the patient swallows a capsule, the doctor will examine if any allergic reaction has occurred. The process is repeated with each and every capsule.

Sometimes, the suspected food can be masked in some other non-allergic food to avoid recognition. The only advantage of food challenge is that the diagnosis can be confirmed quickly.

This is possible when the patient is allergic to the suspected foods alone.

For patients with multiple allergies, this is an expensive test. The procedure is difficult and it requires lot of time. It should be performed only under the doctor’s direction to confirm if the patient is allergic to a food product or not.

Diagnosis can be done further to find out the reason for the patient’s symptoms.

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3. Treatment of Food Allergies
4. AAFA Resources to Help You Tide over Allergy
5. Food Allergies in Infants and Children