Food allergy

What is it?

Food allergy can result in a range of symptoms and is not restricted to the gastrointestinal tract. Some people experience itchiness, numbness or swelling of the inside of the mouth or throat, stomach ache or diarrhoea. Skin symptoms can include itchiness, rashes and hives. Other symptoms can also occur. People with hay fever sometimes react to raw apples, carrots or stone fruit (plums, nectarines). Food allergies can be life threatening if the tongue/throat is affected or if the reaction causes anaphylactic shock. Signs for anaphylaxis are: Swelling in the throat or of the tongue, noisy or difficult breathing, hoarse voice, persistent cough, wheezing, dizziness or collapse, pale skin and floppy body in young children. Allergies can affect people at any age. Skin testing (skin prick test) or a specific serum Immunoglobulin E blood test (ssIgE, formerly knnown as RAST) can help to find the cause. See ASCIA website for more information on appropriate testing for food allergies.

What causes it?

Different underlying immune mechanisms are responsible for the symptoms (IgE mediated, non IgE mediated or mixed). The first contact with a possibly allergenic food does not necessarily cause a reaction. Food particles (protein molecules or fragments) enter the tissues/bloodstream. The body recognises these particles as foreign and builds specific antibodies. The next time the food is touched or eaten the antibodies cause the allergic reaction through inflammatory pathways. A very small amount of the allergenic food will cause a reaction in the allergic person.

Dietetic treatment

In the case of reactions to raw food the treatment would either be eliminating the foods from the diet or cooking the foods. The cooking process changes the structure of the protein fraction. The antibodies then cannot attach to the allergenic components to cause the reaction. With some foods cooking does not change the protein structure sufficiently and the food has to be eliminated (peanut, fish, egg, gluten). If a person reacts severely (anaphylactic shock) to a food care must be taken to prevent food traces (crumbs, smell, steam) touching this person. Kitchen utensils must be cleaned thoroughly, processed foods need to be checked for allergenic ingredients. Sometimes it is difficult to pinpoint the food that causes a reaction. An elimination diet can help in finding food allergens if a person shows only reactions long after ingestion of the allergenic food. Challenges (under medical supervision) with the suspected food/s should be conducted to verify the food allergies.