Evidence check: CYP2C19 in the context of allergy

CYP2C19 is a key drug-metabolizing enzyme, notably for omeprazole and clopidogrel. In the context of allergy, the evidence is weak and inconsistent. Some GWAS have reported modest associations between CYP2C19 variants (e.g., rs4244285, *2) and allergic conditions like asthma or atopic dermatitis, but effect sizes are small and findings are not replicated in larger cohorts. Most data come from population genetics, not clinical trials. Direct-to-consumer tests (e.g., MyBody-X) may list CYP2C19 under 'personalized medicine', but its relevance to allergy is limited. The primary role of CYP2C19 remains pharmacokinetic; altering allergy management based solely on a DTC genetic test is not supported. Evidence: human-moderate (GWAS, observational). Caveat: No RCTs for allergy outcomes. Safety note: Medication adjustments (e.g., PPIs) should be guided by a physician, not by DTC results alone.