Oak Bark
What is it? Overview Usage Side Effects and Warnings

Oak Bark Usage

Written by FoundHealth.

What is Oak Bark Used for Today?

Currently, Germany’s Commission E recommends oak bark internally for treatment of diarrhea and topically for sore throat , mouth sores , hemorrhoids , and eczema . However, there is no meaningful scientific evidence that oak bark offers any therapeutic benefit in these or any other conditions. Only double-blind , placebo-controlled studies can prove a treatment effective, and none have been performed on oak bark. (For more information on why such studies are essential, see Why Does This Database Rely on Double-blind Studies?) Oak bark contains numerous substances in the tannin family, especially ellagitannin, 1 along with potentially active substances in the saponin family. 2 Tannins are thought to have an astringent effect, meaning that they reduce tissue swelling and stop bleeding, and they are traditionally thought to be useful for diarrhea. However, oak bark has never been studied as a treatment for diarrhea. Saponins are often said to act as expectorants, enhancing the ability to cough up phlegm. Again, however, there is no direct evidence that oak bark is useful for coughs or related conditions.

Very weak evidence (too weak to be relied upon at all) hints that oak bark may have value for kidney stones , possibly reducing pain and slowing stone growth. 3 In addition, test-tube studies indicate that oak bark solutions applied topically might have activity against various microorganisms, including staphylococcus, 4 5 and might also exert cancer-preventive effects. 6 However, it is a long way from such studies to actual evidence of clinical benefit.


  1. Konig M, Scholz E, Hartmann R, et al. Ellagitannins and complex tannins from Quercus petraea bark. J Nat Prod 1994;57:1411–5.
  2. Arramon G, Saucier C, Colombani D, et al. Identification of triterpene saponins in Quercus robur L. and Q. petraea Liebl. Heartwood by LC-ESI/MS and NMR. Phytochem Anal. 2002;13:305–10.
  3. Mandana Rodriguez A, Gausa Rull P. Therapeutic effects of Quercus extract in urolithiasis. Arch Esp Urol. 1980;33:205–26.
  4. Voravuthikunchai S, Lortheeranuwat A, Jeeju W, et al. Effective medicinal plants against enterohaemorrhagic Escherichia coli O157:H7. J Ethnopharmacol. 2004;94:49–54.
  5. Gulluce M, Adiguzel A, Ogutcu H, et al. Antimicrobial effects of Quercus ilex L. extract. Phytother Res. 2004;18:208–11.
  6. Cerdá B, Tomás-Barberán FA, Espín JC. Metabolism of antioxidant and chemopreventive ellagitannins from strawberries, raspberries, walnuts, and oak-aged wine in humans: identification of biomarkers and individual variability. J Agric Food Chem. 53(2):227-35.


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