Is MTHFR useful for allergy?

The usefulness of MTHFR for allergy is not supported by strong evidence. MTHFR encodes an enzyme in folate metabolism; variants like C677T can affect methylation capacity. Some observational studies have reported weak associations between MTHFR polymorphisms and allergic conditions such as asthma or atopic dermatitis, but findings are inconsistent and effect sizes are small. The evidence is primarily mechanistic or from GWAS, not from clinical trials. Currently, MTHFR testing is not part of standard allergy diagnostics or management. While adequate folate intake is important for general health, there is no proven benefit for allergy prevention or treatment based on MTHFR status. Caveat: effect sizes are tiny and clinical utility is unproven. Evidence: mixed (mechanistic + weak human studies).