Human Immunoglobulin E (IgE) is a protein with a molecular weight of 190,000 daltons. It is composed of two heavy chains and a pair of light chains linked together by disulphide. A function of IgE is the immunity to parasites. In industrialized countries, IgE has also an important role in allergic reaction (type I hypersensitivity) such as asthma, dermatitis and food allergies. Elevated IgE levels in human serum are also observed in atopic diseases, rare myeloma and disorders related to T cell dysfunction (AIDS for example). IgE levels measurement in serum is mainly useful in the diagnosis, following and treatment of atopic diseases and parasitic infections.