What is food allergy?
It is common for people to believe that all reactions to foods are food allergies. However, allergies to foods affect a relatively small number of people. Less than 1 in 10 children under the age of five and only one or two in 100 adults suffer from true food allergy.
Food allergies are the result of an over-reaction of the immune system to a food protein. The symptoms usually involve swelling, itching, hives or eczema and sometimes anaphylaxis (low blood pressure leading to collapse).
The symptoms are quick to appear (usually minutes but sometimes up to two hours) and, because only one or two foods are involved, most people with this problem know that it is a food and which food is responsible.
Food allergies can be confirmed using a technique known as Skin Prick Testing. An immunologist will generally perform this test which involves placing a tiny drop of a liquid containing the food protein on the skin of the forearm and using a lance to make a tiny scratch. This allows the food protein to come into contact with the antibodies, which lie below the skin surface. (Antibodies are the mechanism which start the allergic reaction in the body.) If antibodies are present, a small welt will appear. If antibodies are not present the skin will be unchanged. There are also blood tests that can detect antibodies to foods.
Having antibodies to foods does not necessarily mean that you have an allergy. For accurate and correct diagnosis, there must also be symptoms, such as those described above, every time the food is eaten.
The more common problem associated with foods is not food allergy, it is actually food chemical intolerance.