Allergy and Intolerance

Food allergy is when the body reacts to certain foods by an abnormal immune system reaction. Some reactions such as "hives" or a red skin rash, swelling of the tongue or lips, happens very quickly.

Other reactions include eczema, vomiting or constipation may be delayed. Reactions can range from mild to severe and there may be overlap between fast and delayed reactions.

Food intolerance happens in a more delayed way, often occurring hours or even days after eating certain foods.The immune system is not involved in this reaction, therefore it is not life threatening and cannot cause anaphylactic shock. Typical symptoms include diarrhoea and vomiting.

Avoiding or reducing the intake of allergenic foods during pregnancy and breast feeding is not proven to prevent an infant from developing food allergies.

The ideal time for starting to introduce solid foods to an infant is after 17 weeks,(4 months) and before 26 weeks (6 months) based on the needs of the mother and child.

Less hypersensitivity has been demonstrated in infants who are weaned before 6 months but there is no ideal time on which all "experts" are agreed.

Allergic or Intolerant?

Many people mistakenly think that they, or their children, are allergic to a particular food substance. A recent report commissioned in the USA, found the field of diagnosis of food allergies is rife with poorly done studies, misdiagnoses and tests whose results are misleading.

So how do you know you have an allergy? True allergies can be demonstrated in a rise of Immunoglobin E antibodies. That said, there are many people with Immunoglobulin E antibodies who do not react to the foods that this suggests. Allergies affect the immune system. Even people who have had genuine food allergies as children, may not have them as adults. Sometimes people develop allergies for unknown reasons. One of the most effective ways of deciding whether there is a food allergy or not, is by using a "food challenge". This involves giving some one a suspect food disguised so that they do not recognise it, or a placebo food. In practice most doctors believe this to be time consuming, and in the case of peanuts for example, there is the possiblity of a frightening response.

For this report Dr. Reidl and his colleagues reviewed all the papers they could find on food allergies published between January 1988 and September 2009, more than 12,000 articles. In the end only 72 articles met their criteria which included having sufficient data for analysis and using rigorous tests for allergic responses.

Intolerances such as Lactose Intolerance, is due to the lack of sufficient enzymes in the body, to digest the sugar in milk. Sulfites in wine, can cause headaches for some, and this is again an Intolerance not an allergy.

During development, the immune system tends to react to certain food proteins, and can produce IgE antibodies, but these antibodies can be transient or inconsequential. By themselves pinprick tests and antibody tests are not sufficient to demonstrate food allergy. The people involved in this study hope that their report will lead to further research and clarify both the definition of, and testing for, food allergies.