The first phase of the immune response occurs when antigens enter the body, usually through the mouth, nose or skin. When this happens, inflammation occurs in the body and the immune system is stimulated to produce more white cells. The task of these extra white cells is to eliminate the offending antigen. If this is successful, the inflammation will subside.

The same process will apply when the body is stressed emotionally or physically. Further stress on the immune system can be caused by an allergic reaction due to the presence in the body of antigens, in the form of allergenic substances.

The second phase of the immune response takes place when the white cells (called leucocytes) are unable to destroy the antigen. The immune system then commences the formation of antibodies, called immunoglobulin, which are tailor-made to combat the antigen and destroy it. Once antibodies have been created to fight a specific antigen, they remain dormant in the body, ready for any future invasion by the antigen. The body now has the capacity to produce more of that antibody, faster, the next time invasion takes place. This is the principle used in immunization and is called Specific Immunity.

Thus, there are two stages to an immune response. The first being, the production of white cells, and the second being, the creation of specific antibodies. Normally, the white cells and the antibodies destroy the antigen and the body makes a speedy recovery. Sometimes however, this does not happen and the result is an allergic reaction which the immune system cannot deal with.

The Allergic Reaction:

There are five different classes of immunoglobulins in the body. These are known as IgG, IgA, IgM, IgD and 19B. IgG is the principal immunoglobulin in the blood and internal fluids. Its job is to remove soluble antigens from the body, in conjunction with other immune complexes. IgA, and to a lesser extent IgM are the main secretory immunoglobulins. They form a protective coating on the body's mucosa, thereby limiting entrance of antigens through the mucosa surfaces, such as in the nasal passages and the gut. Evidently, the physiological functions of IgD and IgE are not fully understood. It is thought that IgE may play an important part in ridding the body of mucosal infection but is ineffective in ecological illness. On the other hand, IgD may act as the trigger to initiate immune responses as it has been observed that, when a mucosal surface is under attack by antigens, initiation of IgE production is dependent upon a lymphocyte that contains IgD.

When the antigen is an allergenic substance (the allergen), the leucocytes and immunoglobulins are unable to cope with it. The antibody and the antigen react, causing a malfunction in the body's defences. The mast cells, which are found in mucous membrane and connective tissue, break up. As a result, chemicals such as histamine, are released and these cause irritation and damage.

Some antigens may reach the bloodstream by way of the body's mucous surfaces. There, they attach themselves to red and white cells or form immune complexes with specific antibodies. These are carried around the body and can cause direct tissue injury, for example a precipitate in connective tissue which can block small blood vessels. This results in fever, aching, muscle pains, and can happen after eating a certain food. Those mysterious, but troublesome, back and joint pains which appear to have no rational cause can be the result of an allergic reaction. Alternatively, the symptoms may not relate to a specific 'target' area. Instead, inflammation and fever may occur over the entire body. This can make it difficult to identify as an allergic reaction.

When inflammation or fever occurs as part of the immune response, it may be localized at an area of infection or be dispersed throughout the entire body. If the latter happens, the body temperature will increase and cause greater enzyme activity. This in turn, increases the metabolic rate; providing extra energy for the production of the leucocytes and immunoglobulins needed to fight the invading antigens. Although, in the case of an allergic reaction, this process is not successful, it may explain why allergy sufferers, particularly of food and chemical allergies, often tend to feel overheated.