OrthoMolecular Natural D-Hist^® is a targeted blend of flavonoids, antioxidants, proteolytic enzymes and botanicals designed to provide comprehensive support for seasonal challenges caused by common environmental allergens. The formula includes quercetin, bromelain, stinging nettles leaf and N-acetyl cysteine. The powerful combination actively promotes healthy nasal and sinus passages for individuals with elevated histamine and respiratory irritation.