How are B12 and allergy related?

The relationship between vitamin B12 and allergies is not well-established in the scientific literature. B12 is essential for immune function, including the regulation of inflammatory responses and homocysteine metabolism. Some observational studies suggest that low B12 levels may be associated with higher IgE levels or increased risk of allergic sensitization, but the evidence is largely mechanistic or based on small cohorts. There are no robust randomized controlled trials demonstrating that B12 supplementation prevents or treats allergies. Consumer DNA or lab tests that claim a direct link between B12 and allergies often overstate the evidence. Allergies are multifactorial, involving genetics, environment, and microbiome, so B12 is unlikely to be a primary driver. A B12 deficiency should be diagnosed and treated by a healthcare professional, but it should not be considered a treatment for allergies. Safety note: B12 supplementation is generally safe, but self-medicating without medical guidance is not advised. Overall, the evidence for a strong B12–allergy connection is weak and unclear; more research is needed.