How are IgG and Müdigkeit related?

The relationship between IgG antibodies and fatigue is scientifically unclear. IgG, particularly IgG4, is often marketed in the context of food sensitivity testing, with claims that immune activation against foods can cause chronic fatigue. However, the evidence is weak: no robust randomized controlled trials confirm a causal link. Fatigue has many causes—sleep deprivation, iron deficiency, thyroid dysfunction, etc. IgG food sensitivity tests are not recommended by major allergy societies (e.g., EAACI) because they frequently yield false positives and may lead to unnecessary dietary restrictions. A positive IgG result typically reflects exposure, not intolerance. For persistent fatigue, a medical workup (CBC, CRP, ferritin, thyroid panel) is advised before interpreting IgG tests. The evidence here is best classified as 'mechanistic' or 'unclear'—plausible biological pathways exist, but clinical proof is lacking.