The total IgE test measures the overall level of immunoglobulin E (IgE) antibodies in the blood. It is primarily used to diagnose allergic disorders, assess immune system function, and guide treatment for conditions like asthma and allergic reactions. While the total IgE test indicates the presence of IgE antibodies, it does not specify what a person is allergic to, and many individuals with subtle allergies may have normal total IgE levels.