What role does IgG play in Müdigkeit?

The role of IgG in fatigue is scientifically controversial. IgG antibodies are often marketed in 'food sensitivity tests' that claim to explain chronic fatigue through dietary triggers. However, current evidence indicates that elevated IgG levels to foods are usually a sign of normal immune exposure, not intolerance or allergy. Rigorous studies linking IgG to fatigue are lacking. In clinical immunology, IgG subclass measurements are used for recurrent infections or immunodeficiency, not for fatigue workup. A true IgG deficiency can increase infection risk, which may indirectly contribute to fatigue, but this is rare and requires specialist evaluation. In conditions like ME/CFS, IgG changes have been observed as epiphenomena, not causative. Conclusion: IgG testing for fatigue is not evidence-based. Patients with persistent fatigue should first investigate common causes (iron deficiency, thyroid dysfunction, sleep apnea, mental health) before considering IgG.