Biologically active substances of oak are concentrated in its bark. Most often, oak bark is used as an anti-inflammatory agent - both for external and internal use. This is possible due to its astringent action and protein denaturation process. Due to the fact that oak bark relieves inflammation, heals and uses an anti-putrefactive effect, it is actively used in dentistry for the treatment of gingivitis, stomatitis, periodontal disease, flux. In the form of lotions, oak bark is used for eczema, cracks, burns and other skin diseases. The content of gallic acid and its derivatives explains the disinfecting, anti-hemorrhagic and anti-radiation properties of oak bark. Due to its antifungal and antiseptic effect, foot baths are prepared from oak bark with increased perspiration. The same procedure is helpful for sweating hands. Infusions or decoctions are used orally as prescribed by a doctor in the complex therapy of diarrhea of various origins, gastritis and peptic ulcer disease, colitis and enterocolitis, bleeding from the digestive system. Oak bark is contraindicated for use in the presence of hypersensitivity to its biologically active substances. It is also prescribed with caution to those who have had liver and kidney problems and have a tendency to constipation.