White Oak Bark, which comes from the Quercus alba tree, is a hardwood tree native to the Eastern United States. Its wood resists rot; certain of this wood is commonly used for making wine barrels.

Its high tannin content gives white oak an astrigent quality; it has been used to reduce bleeding in the mouth, to treat diarrhea, and as a first aid herb.* White oak has been researched as a treatment for urinary tract infections and kidney stones, supported by its traditional use as a diuretic and cleansing tonic of the liver and kidney. Also owing to its astringent tannins, white oak is a useful expectorant (encouraging the expulsion of phlegm from the lungs) and skin cleanser.*