What role does Vitamin D 25-OH play in Allergie?

Vitamin D (25-OH) plays an immunomodulatory role that may influence allergies. Low vitamin D levels are associated with increased risk of allergic conditions such as asthma, eczema, and hay fever, especially in children. Vitamin D regulates T-cell and dendritic cell function, potentially dampening allergic inflammation. However, evidence is mostly observational; randomized controlled trials show inconsistent results. Some supplementation studies report symptom improvement, others do not. The optimal 25-OH level for allergy prevention remains unclear. Testing for vitamin D deficiency is reasonable in allergy patients, but a normal level does not rule out allergies. Evidence is moderate: plausible mechanisms and epidemiological links exist, but strong causal proof from RCTs is lacking. Correcting a deficiency may support overall immune health, but should not replace standard allergy management.