What is a food allergy?

A food allergy is an immune system response to a food that the body mistakenly believes is harmful. Once the immune system decides that a particular food is harmful, it creates specific antibodies to it. The next time the individual eats that food, the immune system releases massive amounts of chemicals, including histamine, in order to protect the body. These chemicals trigger a range of allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system.

Do you suspect your child has a food allergy?
If you can answer yes to all or most of the questions below, it is highly likely your child has a food allergy. It is important to seek medical advice for further testing.


* Note: Reactions can also occur through skin contact or inhaling the food (some foods become airborne when cooked eg egg, fish,peanuts)

Symptoms
Symptoms are often severe, and may even be life threatening.
They can range from a tingling sensation in the mouth, swelling of the tongue and throat, diarrhoea, vomiting, excema, asthma, urticaria (hives), rhinorrheaa (nasal drip), abdominal cramps, angio-oedema (swelling of areas of the skin) and in extreme cases, anaphylactic shock (total collapse).
Symptoms typically appear within minutes to two hours after the person has eaten the food to which he or she is allergic.
Anaphylaxis
Hives (acute urticaria) and angioedema (swelling of the eyes, lips, tongue) frequently occur in people with food allergy. The onset of symptoms may be rapid, within minutes after eating the offending food. Foods most often responsible are raw meats, fish, vegetables and fruits


Diagnosis
Skin Prick Test
RAST blood test


Treatment
The treatment for food allergy is strict avoidance of the offending food(s). Reactions can sometimes be avoided or reduced by the use of anti-histamines, or by desensitising therapy, but essentially, people who are allergic to a food should avoid all contact with that food.

Most common foods that cause an allergy
In Australia the most common foods are milk, soy, egg, peanut, wheat, fish, tree nuts.
People with food allergies typically react to one or two foods.

Allergy is produced by a combination of susceptibility and exposure.
Food allergies are usually due to the protein component of the offending food. For some reason some of the food protein is absorbed from the intestine intact, instead of being digested as most proteins are. Once the intact protein is in the blood stream, it is recognised as a foreign protein to the body, or in other words as an antigen. The body produces antibodies (usually immunoglobulin E) to this antigen, and the immunoglobulin binds the antigen to form an antigen-antibody complex.
This antigen-antibody complex travels around the body and stimulates certain cells, called mast cells, to burst open and to release substances which mediate an allergic reaction. Histamine is an example of such a mediator. Histamine causes an inflammatory response in the cells that it reaches, and this inflammatory response is what causes the symptoms of the food allergy.

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