Antibodies are substances made by the body's immune system in response to unwanted and dangerous 'invaders' such as viruses or bacteria. Antibodies attach to the foreign substances so the immune system can destroy them.  Immunoglobulin E (IgE), for example, is a class of antibody. The five major types of antibodies are:

• IgA -  IgA antibodies protect body surfaces that are exposed to outside foreign substances.

• IgG  - IgG antibodies are found in all body fluids. They are  very important in fighting bacterial and viral infections.

• IgM -  IgM antibodies are the largest antibody. They are found in blood and lymph fluid and are the first type of antibody made in response to an infection. They also cause other immune system cells to destroy foreign substances.

• IgE -  IgE antibodies are found in the lungs, skin, and mucous membranes.

• IgD -  IgD antibodies are found in small amounts in the tissues that line the belly or chest. 'How they work is not yet clear'.

The levels of each type of antibody can give your doctor information about the cause of a medical problem.