Is IgE useful for fatigue?

IgE (immunoglobulin E) is primarily involved in allergic responses. Elevated IgE levels can indicate allergies such as hay fever or asthma, which may indirectly contribute to fatigue through sleep disruption (e.g., nocturnal symptoms) or chronic low-grade inflammation. However, IgE is not a specific or sensitive biomarker for fatigue itself. Fatigue is multifactorial, with causes including iron deficiency, thyroid dysfunction, sleep apnea, depression, and infections. Therefore, measuring IgE is not routinely recommended in a general fatigue workup unless allergy symptoms are present. The evidence is mixed: in patients with allergic symptoms, IgE testing can help identify an allergic component, but as a standalone fatigue marker it lacks utility. Caveat: normal IgE does not rule out allergies; elevated levels require clinical correlation and do not automatically explain fatigue. Without concurrent allergic signs, IgE adds little value for fatigue assessment.