How are CYP2D6 and Allergie related?

The relationship between CYP2D6 and allergies is indirect and primarily drug-metabolism related. CYP2D6 metabolizes many antihistamines (e.g., promethazine, some beta-blockers) and other allergy medications. Genetic variants (poor metabolizers) can lead to higher drug levels and increased side effects. Some studies have explored links between CYP2D6 polymorphisms and risk for asthma or allergic rhinitis, but results are inconsistent and effect sizes small. The evidence does not support clinical use for allergy risk prediction. Direct-to-consumer tests often overstate the relevance. The main practical implication is pharmacogenetic: if you know your CYP2D6 status, discuss dosing of relevant allergy drugs with your doctor. Safety note: Never change medication based on a DTC test alone.