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Diagnosing Food Allergies

There are some specific things that a doctor can do to help you discover if the cause of your symptoms is a food allergy. The doctor can utilize a questionnaire, a physical exam, study a food journal kept by the patient, scratch skin test results and use a food elimination diet.

The Questionnaire:

A doctor may give the patient a questionnaire to fill out. The answers are then used to determine if there is a pattern that would suggest a food allergy. The results of the questionnaire will help decide if more tests are needed. Some common questions asked on this type of questionnaire are:

What reaction did you have that you suspect is from a food allergy?

When did the reaction occur, how long after eating the food?

Did anyone else get sick who had eaten the same food?

How much of the suspect food did the patient eat before a reaction was noticed?

Was the food raw or prepared?

Were there other foods that were eaten at the same time?

Does the patient suffer from other conditions that may be attributed to food allergies such as ear infections, eczema, or asthma?

Food Diary:

A food diary is simply a record of everything the patient eats and a note of any reactions that the patient experiences after the meal or snack. The patient and doctor sit down and read the diary making note of anything that suggests a pattern of food allergic reaction.

Elimination Diet:

An elimination diet is a tool used to determine if a specific food allergy is likely. The doctor will instruct the patient not to eat a particular food for a certain time period. If the symptoms go away when the patient does not eat the food and then when the food is reintroduced into the diet the symptoms return, the doctor can then have an idea about what is causing the reaction. The doctor may do this pattern with several foods.

The doctor may wish to measure an allergic reaction by using a scratch skin test. These tests are quick, simple, and relatively safe. The doctor will match a positive skin scratch test with the patient's own history of having a reaction to that particular food. It is possible to have a positive skin test without having a reaction to eating that food. The danger in skin scratch tests occurs when the patient has a severe reaction to the skin test called an anaphylactic reaction, which can be dangerous, even deadly.

There is also a method called a double-blind food challenge. Foods suspected of causing a food reaction is placed in opaque capsules are swallowed by the patient and the doctor watches for a reaction to occur; the process is repeated for each suspected food. Individuals with a history of severe reactions should not take this method. The method is called double blind because neither the doctor nor patient are aware of what food substances are in which capsules.