Evidence check: B12 in the context of Allergie

The provided context does not contain direct evidence linking vitamin B12 to allergies. B12 is known to be involved in homocysteine metabolism and DNA methylation, which may theoretically affect immune regulation, but specific studies on allergies are absent here. Consumer DNA or microbiome tests claiming a connection between B12 and allergy risk are not supported by robust clinical evidence. The evidence is unclear; supplementation without medical guidance is not advised.