Getting to know

If you have experienced an adverse reaction to food, you should consult a doctor. As mentioned above, not all food adverse reactions are allergic in origin and the treatment for food allergy, food intolerance or food poisoning are quite different.

The first thing the doctor will want to know is an accurate history of your problem. It is important to tell him all the symptoms you have experienced; the conditions in which they appeared; all the foods and drinks you were having at the time and the way the the food was cooked. Try to recall how much time elapsed from the ingestion of food until the occurrence of symptoms. Have you have experienced these symptoms before when eating the same food or food cooked in the same way? Perhaps they occurred when eating in the same place or the same situation (like for example symptoms appearing during a certain season of the year, when you are performing certain activities etc). 

The doctor will probably want to perform some allergy tests on you to determine if your symptoms are caused by a food allergy or not. There are several types of test for diagnosing food allergy.

• A drop of a solution containing the food allergen is placed on the skin of the forearm and then the skin is very finely punctured through the drop. Numerous foods can be tested simultaneously using this test. The results are read in 15-20 minutes. A swollen, red, itchy reaction at the puncture site is usually an indicator of a positive response. If the tests are negative (no reaction appears at the puncture site) the test food can be ruled out as the cause of your symptoms. However, a positive test result does not necessarily mean that your symptoms are caused by that food. The meaning of a positive reaction is that you have the potential to develop allergy to that food (your body is producing IgE antibodies which react to that specific food). There are a lot of people who, if tested, would show positive reactions to a range of foods without ever having had any symptoms when eating those foods. (If you want to know how this is possible please read the section  What is allergy – Sensitization). A positive result must be interpreted in relation to the clinical history and other test results that the doctor might have performed on you. Typically, a positive test is followed by more detailed investigations. This is why it is unwise to try to make your own diagnosis using commercially available home allergy tests -. you might come to the wrong conclusion!
• In some cases the skin prick test cannot be performed. However the doctor can still check if you are producing IgE antibodies against a particular food by measuring them in your blood. He will have to take a blood sample from you to perform this test. As with the skin prick tests, a negative result practically rules out an allergy to the food in question whereas a positive test may implicate the food as being responsible (at least in part) for your symptoms.     

• In some cases, particularly when the food is suspected to cause allergic eczema or contact urticaria, the food allergens are simply applied to the skin for a specific time without the skin being punctured. In these tests, allergen solutions or raw foods can be used. For the diagnosis of contact urticaria, the allergens are left on the skin for up to 30 minutes. If a swollen, red, itchy reaction occurs at the contact area, the test is considered positive and the food is recognised as the cause of the symptoms. If the food is suspected to cause atopic dermatitis, the allergens are left on the skin for up to 48 hours. The appearance of an eczema-like reaction (redness, swelling, blisters and eventually crusts) at the site where allergen was applied indicates a positive test and a very high probability of the food to being the cause of the symptoms.    

• This will be recommended if the doctor, after performing all the tests mentioned above, still cannot decide if the food is the real cause of your symptoms. To perform this test the doctor will ask you to eat a small quantity of the suspect food and then he will record any symptoms that you might experience. If after a 30-60 minutes interval you didn’t develop any symptoms you will be asked to eat a slightly greater amount of the food and the doctor will monitor you for the same period of time. The same steps can be repeated 5-6 times a day, with increasing amounts of food. If the test remains negative (you don’t develop any symptoms) then the food is excluded as a cause of your problems. If during the test you develop symptoms similar to the ones that prompted you to see the doctor, the food is identified as the underlying cause. The oral challenge test is the most sensitive tool for diagnosing food allergy. However, due to the fact that it can trigger severe allergic reactions (particularly in people with food anaphylaxis) this test is only conducted in hospital and under close medical supervision and only when the history and the other tests are inconclusive.