Food allergy

This fact sheet is for people who have, or suspect that they have a food allergy.

Most people have a bad reaction to a food at some point, and some may worry that an allergy may be responsible.

Food allergies in young children are more common than in adults, but most children outgrow these by school age.

True food allergies

With true or 'classic' food allergies, a problem food triggers the immune system, producing a response to the food that can cause severe and even life-threatening symptoms. It's important that if you think you have a true allergy to a food you get it diagnosed by a doctor, so that you can avoid it and prevent further allergic reactions.

Having a tendency to allergies (atopy) is partly inherited. If eczema, asthma, or hay fever run in your family, you're more likely to have allergies.

Is it really a food allergy?

Food allergy is sometimes confused with a food intolerance or food poisoning, which do not involve an immune response. These can make you feel ill, and may be dangerous, but they are not usually harmful in the same way that a true food allergy might be (see Symptoms and Food intolerance for more details).

Food and the immune system
There are two components involved in a true allergic reaction. The first is the production of immunoglobulin E (IgE), an antibody that circulates in the blood attacking things such as germs. The second is the mast cell, a type of cell that is found in the body at places where allergic reactions occur, including the nose, throat, lungs and skin.

If you have a food allergy, your body mistakes certain foods as harmful, and produces IgE antibodies. This is known as sensitization and may not cause many, if any, symptoms. However, the next time you eat the food, the IgE is ready to react with the food. This causes mast cells to release chemicals such as histamine, which leads to a range of physical symptoms that is called an allergic reaction.

Symptoms

The first symptom of an allergic reaction to food is often itching and swelling in the mouth, tongue and throat. You may also get some or all of the following symptoms:

skin reactions, such as swelling and itching, eczema and flushing,Urticaria, vomiting and/or diarrhoea
coughing, wheezing or a runny nose
swelling of the lips
sore, red and itchy eyes
Allergic reactions usually happen within a few minutes of eating food that you are allergic to, but they can take several hours to develop.

Some people develop a severe, whole-body allergic reaction called anaphylaxis, or anaphylactic shock. This is a rare but potentially fatal allergic reaction where the symptoms develop all over the body, causing swelling, loss of consciousness, low blood pressure and breathing problems.

Problem foods

In adults, the most common food allergies are to peanuts, tree nuts (such as walnuts and hazelnuts), fish and shellfish. Foods which commonly trigger allergies in children include cows' milk, eggs, peanuts, soya, wheat, tree nuts, fish and shellfish.

Food intolerance

This type of response to a trigger food may develop over a number of hours or days. Food intolerance's are sometimes caused when you aren't producing enough of the natural digestive chemicals to break down a particular type of food, although often the cause remains unknown. Symptoms of food intolerance include diarrhea and flatulence. The most common food intolerance's are to lactose (the sugar found in milk) and gluten (this is called coeliac disease).

Diagnosing and food allergy

1. Modified skin allergy test

2. Serum testing(allergy testing with blood)

Treatment

ORAL Immunotheraphy.