Description. Oak bark is widely used as an effective astringent. Oak bark is rich in galic and ellgalic acids, quertecin, flobaphen, pictines and tannins. Tannins are thought to have an astringent action, meaning that they reduce tissue swelling and stop bleeding, and they are traditionally thought to be useful for diarrhea. It has antiphlogistic, haemostatic, and antiseptic properties. Oak bark is often used topically for various skin disorders. Use. Currently herbalists recommend oak bark internally for treatment of diarrhea, gastric and intestinal bleeding; and topically for sore throat, mouth sores, hemorrhoids, and eczema, burns, acne, hemorrhoids and bedsores. An important healing component in the smooth bark of the oak tree is its tannin, which has astringent and mildly antiseptic qualities. The tannin is what makes oak bark valuable for minor wounds and inflammation, for tightening tissue and lessening oozing. Oak Bark water infusion is an effective wash for uro-genital diorders. Attention! Before using any herbal products, make sure that you have full knowledge of how the herb works and any adverse reaction it may cause.