Since the 19th century, American eclectic physicians have valued vitamin C- and tannin-rich blackberry leaves for their astringent qualities, infusions of which have proven useful in treating diarrhea, dysentery, hemorrhoids, and sore throat, among other afflictions. Use of blackberry leaf tea for the treatment of diarrhea and inflammation of the mucous membranes of the mouth and throat has been approved by the German government. Strong infusions of blackberry leaf have been shown to reduce blood sugar levels.