Historically, Total IgE measurement on a blood sample was used as an entry level test to identify allergy prone patients. However over the years it have become apparent that Total IgE levels can vary in both allergic and non allergic individuals. Some patients with significant nasal allergies may in fact have relatively low Total IgE, whilst those with extensive eczema of the skin will have very high Total IgE even if they have no allergy at all. Total IgE can also be raised with an underlying parasite infection. Some individuals may have a Total IgE of several hundred units but have no allergy at all. Total IgE measurement can therefore confuse the diagnostic process and should not be used as an entry level allergy screening test. It is far more useful to do Specific IgE blood testing for suspected allergens after taking a thorough allergy history from the allergy sufferer.