What exactly constitutes an allergy is the subject of much debate. The word itself is only ninety years old, and was first used by Baron Clemens Von Piquet in 1906 to describe 'altered reactivity'. Von Piquet was a doctor, a paediatrician, who needed a word to describe the observations he had made about young patients and their reaction to the environment.

He also introduced the word allergen to describe the substance, which brought about the allergic reaction.

Although these observations were made little was known at that time about how the reaction arose. In 1925 the word allergy was narrowed down to mean a substance that was capable of provoking a response in the immune system. Experiments showed that a reaction to pollen or food could be passed from one person to another by injecting a small amount of blood serum under the skin. The area around the site of the injection went red and became sensitive to the allergen, this was evidence that that the immune system was involved. Just how the immune response worked was explained further by the discovery of Immunoglobulin E [IgE] in the 1960s.

Here is a brief explanation of how IgE works by leading allergist Professor Jonathon Brostoff: 'An antibody is a protein molecule made by the body to combat disease causing bacteria and viruses. The antibody binds to a specific target known as its antigen. This target is usually a chemical located on the virus or bacterium, so the net result is that the antibody binds to the invader. The bound antibodies are rather like accusing fingers pointing at the invading microbe, in that their presence arouses the body's immune cells to attack the microbe.

What goes wrong in an allergy, is that the body makes IgE antibodies in response to a harmless antigen, such as a food molecule. IgE antibodies are usually found on the surface of special immune cells known as mast cells that occur in tissues throughout the body.

If the molecules on the surface of a mast cell bind to their specific antigen they stimulate the mast cell to release several chemical messengers. The normal purpose of these chemicals is to organise a more effective immune response, but in sufficient quantities they can produce the damaging symptoms of allergy. The Antigen that causes such a reaction is known as an allergen.'

The Classical definition therefore of what actually constitutes an allergy is when the patient has an IgE- mediated response to an allergen. There is however a grey area, as there are other mechanisms which may be responsible for food sensitivities. Sometimes a reaction to food is known as a food intolerance, to indicate that although there is no IgE response, the body is reacting to something, which has been eaten in an unacceptable way.

Allergy problems seem to be becoming increasingly common; atopic disease such as Eczema, Asthma and Hayfever have reached epidemic proportions in our children, and food sensitivities can be responsible for a wide spectrum of complaints including infant colic, recurrent diarrhoea, nettlerash, headaches, and hyperactivity.

If you think that an allergy may be responsible for your child's health problem what can you do about it? The first thing is to see whether your instincts are correct and to have them allergy tested. There are several ways in which to do this:

• RAST
  Your GP can send you for a test known as a RAST [radioallergosorbent test]. This is a test, which measures the IgE response a person has to a food protein or pollen. This can be very useful in confirming an allergic reaction, but as previously mentioned it would not cover intolerance's that arise via a different mechanism

• Skin Prick Test
  This is a very common test for allergy which looks at the reaction of the skin to a range of common allergens, or to one specific allergen if there is a strong suspicion of it. However, confirmation is needed.
  
  A drop of the allergen is placed on the arm and scratch or prick is made in the skin underneath the drop. A minute amount of the allergen will enter the skin and if the patient is sensitive to it there will be a marked skin reaction known as a ‘Wheat and flare ‘ response. Again, the skin prick test is not foolproof as foods to which the patient is intolerant may cause a local reaction, possibly in the gut. IgE antibodies can sometimes be detected in the affected part of the body, but they do not enter the blood stream and so will not affect the skin.

• Cytotoxic Testing
  This involves taking a blood sample from the patient and extracting the white blood cells from it. These are then exposed to the suspected allergen. If the patient is sensitive to the substance in question there should be a reaction in the white blood cells, visible through a microscope. In carefully controlled tests this method has proved around 80% effective. Again not foolproof, but gives a reasonable degree of accuracy.

• Elimination Diets
  The idea behind an elimination diet is to restrict the intake of the suspected allergens for around a three-week period. This will often make the patient feel worse for about the first week, then should be followed by a marked improvement. The foods should then be reintroduced one at a time, and their effect noted. Elimination diets can be very effective. Even if your allergy is to a staple food such as wheat, milk or gluten, due to an increase in demand alternatives to these foods can be found in nearly every supermarket or health food store. With a little forward planning any food can be avoided, where necessary, with the minimum of effort.

• Vega Test
  In this test a weak electrical current is passed into the patient's body through an acupuncture point at the tip of the finger and an electrical reading is taken from the point. A Phial containing the allergen is introduced into the electrical circuit, and when sensitivity occurs the electrical resistance at the acupuncture point will change. The main drawback with this system is that it relies on the skill of the practitioner to a greater extent than any other test. The point must be located accurately and the correct amount of pressure must be maintained throughout the test.

• Applied Kinesiology
  This is an approach that involves the measuring of the strength of certain muscles, before and after the presence of the suspected allergen. The theory is that the presence of an allergen will cause a weakness in the energy field of the body. The practitioner will test the resistant strength of a muscle then place the suspected allergen either in the hand or under the tongue and immediately retest the muscle. Any diminution of strength may indicate intolerance to the substance being tested. Whilst this is not exactly a scientific test, it does seem to produce good results for a number of people.

The Orthodox View

Allergies are usually treated by a program of desensitisation. Placing a small amount of the substance either sublingually (under the tongue) or intra dermally (under the skin) carries this out. This is sometimes called a provocation-neutralisation technique. The amount of the allergen is carefully measured and increased until the patient responds in their characteristic way with symptoms of the allergy. This is the provocation part. The dose is then given in smaller amounts than the patient will react to, to gradually desensitise them to the allergen, this being the neutralisation part. This technique can work well but it leaves the under lying weakness in the immune system untouched.

The Alternative View

If allergies are definitely at the root of your child's health problem, the long-term solution may be found in an alternative approach. Homeopaths for example would not require that you scrupulously avoid the allergens. For one thing this may be impossible if the substance is dust mite or pollen. For another the necessary diet avoiding the food allergens may be so restrictive that it is too difficult to follow, or so limited that it may lead to your child not getting a sufficient supply of necessary vitamins and minerals. The Homeopath would take the view that the allergy is just a symptom of a deeper disturbance in the immune system. A healthy person should not react to an innocuous substance as if it were a harmful invader, the approach would therefore be to strengthen the immune system and eradicate the allergy so that life could be lived to the full with out troublesome dietary restrictions. This is entirely possible and many Homeopaths have case histories that can attest to its efficacy in the treatment of allergies.