lgE is a cytophilic antibody that has been associated with allergic reactions, parasitic diseases and skin sensitization. lgE is mainly derived from plasma cells in the submucosa of the respiratory and digestive tracts. There is another specific lgE which has high specificity and sensitivity and is important in the diagnosis of allergic asthma and the search for allergens. The collection method is serum extraction. The normal value of serum immunoglobulin E (IgE ) is 0.1~0.9 mg/L. Strongly positive for total IgE and negative for specific IgE are normal results. If the test result suggests an abnormality, the diagnosis of allergy must also be made in conjunction with the clinical history and other diagnostic tools. It is important to note that the use of anti-allergy medications and certain cold and flu medications containing anti-allergy ingredients will affect the results. Therefore, it is recommended to stop taking medication for at least two days before performing the in vitro allergy test.