What does low immunoglobulin E indicate?

IgE refers to immunoglobulin E, a special type of antibody primarily involved in mast cell-mediated immune responses. It is an antibody that acts specifically against antigens. Under normal circumstances, IgE levels in human serum are very low. Since IgE is predominantly found in individuals with allergic reactions, the measurement unit is typically kU/L, with effective values ranging from less than 0.34 to 25.7. If the measured value is below 120–150 kU/L, it indicates that the patient's IgE level is within the normal range and an allergic reaction is unlikely. However, in some cases, the test results may show abnormally low values, or other biological factors involved in IgE reactions may change, leading to reduced IgE levels. Therefore, if a patient exhibits signs of allergy, further investigation is necessary to determine the underlying cause—even when IgE levels are within the normal range—so that appropriate treatment and preventive measures can be provided.