Is Vitamin D Test useful for allergy?

A vitamin D test has limited utility for allergies. While vitamin D modulates immune function and deficiency is linked to higher allergy risk, there is no strong evidence from randomized trials that testing or supplementing based on levels improves allergy outcomes. The evidence is mostly observational and mechanistic. Testing may be reasonable if deficiency is suspected (e.g., low sun exposure), but it is not a specific allergy diagnostic tool. Results should be interpreted with clinical context. Caveat: routine vitamin D testing for allergy is not evidence-based.