Oak bark
Tanner’s bark; the bark of the common or English oak, Quercus robur of Linnaeus, which the European monograph takes together with the sessile oak, Quercus petraea, and the downy oak, Quercus pubescens; in pharmacy Quercus cortex; the Greek drus of Dioscorides
- Known today as
- The bark of the common oak, collected in spring from young trees, dried in the sun, greyish and somewhat polished outside and brown within. Grieve describes it as “slightly tonic, strongly astringent and antiseptic,” with a strong astringent bitter taste and a slightly aromatic smell. The galls of the oak have an entry of their own, Oak galls.
- Kind
- Plant, in 2 older authorities
- Constituents
- tannins, gallic, ellagic acid
- Earliest authority here
- Dioscorides (c. AD 40–90)
- In other databases
- Plants of the World Online · GBIF · Wikidata
Caution. Because it can slow the absorption of medicines taken at the same time, the European agency advises taking it at least an hour before or after other medicines. Not for anyone under eighteen, for want of data. As a bath it is not for open wounds, large injuries to skin or mucosa, or infections of them, and hot baths are not for fever, infection, heart failure, or high blood pressure. Recurrent diarrhoea, bloody stools, or rectal bleeding call for a doctor. Allergic reactions have been reported.
Oak bark: what was it used for?
The astringent of the hedgerow, given for diarrhoea, dysentery, and bleeding. Grieve has the decoction taken in wineglassful doses in chronic diarrhoea and dysentery, used as a gargle in chronic sore throat with a relaxed uvula, and applied to bleeding gums and piles; she reports it once given as a substitute for quinine in intermittent fever, and powdered and inhaled in early consumption, “Working tanners” being, she says, well known to be particularly exempt from that disease. The bark tanned leather everywhere, and dyed wool purplish with copperas and black with iron.
Oak bark: what does modern science say?
The European Medicines Agency’s herbal committee accepts oak bark as a traditional herbal medicine, “exclusively based upon long-standing use,” for the symptomatic treatment of mild diarrhoea, of minor inflammation of the mouth or the skin, and of the itching and burning of haemorrhoids once a doctor has excluded anything serious (monograph of 2010). Its assessment report puts the bark’s tannins at a highly variable 8 to 20 per cent, both the hydrolysable kind that yield gallic and ellagic acid and the condensed kind, the amount depending on the time of harvest, the age of the branches, and the method of assay.
Pharmacognosy & Toxicology
- Constituents
- tannins8 to 20 per cent, both hydrolysable and condensed
- gallicyielded, with ellagic acid, by the hydrolysable tannins
- ellagic acid ChEMBL
- Mechanism
- An astringent: Grieve calls the bark “strongly astringent”; the European agency notes it can slow the absorption of other medicines taken with it.
- Standing
- European Union herbal monograph (2010): traditional use, “exclusively based upon long-standing use,” for mild diarrhoea, minor inflammation of the mouth or skin, and haemorrhoids.
- European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Quercus cortex (Oak Bark). EMA/HMPC/3203/2009, 25 November 2010. Read in full · the text read
- European Medicines Agency, Committee on Herbal Medicinal Products. Assessment report on Quercus cortex. EMA/HMPC/3206/2009, 25 November 2010. Read in part · the text read
- Grieve, M. A Modern Herbal, “Oak, Common.” As published on botanical.com. Read in full · the text read
Constituent names open the compound’s record at PubChem, and “ChEMBL” beside a name opens its record at ChEMBL, the European Bioinformatics Institute’s database of bioactive molecules. Where a mechanism line was checked against ChEMBL (ChEMBL 37, read 1 October 2026), the check is shown with the measured value and its source paper, or says plainly that nothing has been measured. Doses are as the references give them, for description only; this is not medical advice. Each source carries the result of its check against Crossref, PubMed, or the authority’s page: see Verification.
Oak bark: what lore surrounds it?
“The Greeks held the Oak sacred, the Romans dedicated it to Jupiter, and the Druids venerated it.” In England, Grieve writes, Gospel Oaks marked the parish bounds, where the clergy stopped to read the Gospels in the yearly procession; the country proverb set the leafing of oak against ash to forecast the rain; and in South Wiltshire villagers wore oak on the 29th of May and claimed their right to fallen wood with the shout of ‘Grovely, Grovely, and all Grovely!’ She records the great trees, the Fairlop Oak of Hainault Forest at 36 feet round, the Newland Oak of Gloucestershire at 46, and reports that Philip of Spain ordered the Armada to burn every oak in the Forest of Dean. A superstition held that whoever cut or maimed Abraham’s Oak at Mamre would lose his firstborn son.
Oak bark: what did the older authorities say?
- Dioscorides
- Every part of the oak is astringent, he says, but the film between bark and wood, like the skin under the acorn’s cup, is the best for the bowels: boiled and drunk for dysentery and for spitting of blood, and pounded into pessaries for excessive discharges of the womb. Acorns are diuretic, and a decoction of them and the bark in cows’ milk helps against poison.
- Nicholas Culpeper
- “Jupiter owns the tree.” The leaves, the bark, and the acorn cups “do bind and dry very much,” and the inner bark and the thin skin of the acorn stay spitting of blood and the bloody flux. Hippocrates, he writes, used the fumes of oak leaves on women troubled with the strangling of the mother, “and Galen applied them, being bruised, to cure green wounds.” The water found in the hollows of old oaks is “very effectual against any foul or spreading scabs.”
Sources
- Grieve, M. A Modern Herbal, “Oak, Common.” As published on botanical.com. Read in full · the text read
- Culpeper, N. The Complete Herbal, “The Oak.” Project Gutenberg, 49513. Read in part · the text read
- Dioscorides. De materia medica, 1-142 and 1-143, in the modern English version of T. A. Osbaldeston and R. P. A. Wood (Johannesburg: Ibidis, 2000), after Goodyer’s translation of 1655. Internet Archive. Read in part · the text read
- European Medicines Agency, Committee on Herbal Medicinal Products. European Union herbal monograph on Quercus cortex (Oak Bark). EMA/HMPC/3203/2009, 25 November 2010. Read in full · the text read
- European Medicines Agency, Committee on Herbal Medicinal Products. Assessment report on Quercus cortex. EMA/HMPC/3206/2009, 25 November 2010. Read in part · the text read
Verification
- Checked
- October 1, 2026
- Passes
- Every sentence read against its sources, in the pass over the remaining 343 entries
- The Standing line checked against the authority it names (EMA, WHO, FDA, CITES, Commission E)
- Every dated or regulatory claim checked by category across the database
- Sources
- 5 cited: 2 read in full, 3 read in part.
- Corrections
- None were needed.
What was checked, how, and what was found is set out on the Verification page. A checked source is one whose record was found; it does not make the entry medical advice.
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Cite This Entry
Version 1 · first published October 16, 2026
- Chicago
“Oak bark.” In Materia Medica, edited by B. C. P. Statema. Version 1. The Thinking Press, 2026–. Last modified October 16, 2026. https://thethinkingpress.org/materia-medica/oak-bark.
- MLA
“Oak bark.” Materia Medica, edited by B. C. P. Statema, version 1, The Thinking Press, 16 Oct. 2026, thethinkingpress.org/materia-medica/oak-bark. Accessed 17 Oct. 2026.
- APA
Oak bark. (2026, October 16). In B. C. P. Statema (Ed.), Materia medica (Version 1). The Thinking Press. Retrieved October 17, 2026, from https://thethinkingpress.org/materia-medica/oak-bark
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See Also
Sharing tannins, ellagic acid
Rosa gallica · Botrychium lunaria · Rheum officinale · Pulmonaria officinalis · Punica granatum · Bistorta officinalis · Fragaria vesca · Bezoar stone
Also in Dioscorides
Oat in Dioscorides · Mullein in Dioscorides · Opium poppy in Dioscorides · Milk thistle in Dioscorides · everything Dioscorides names →
Also in Nicholas Culpeper
Periwinkle in Nicholas Culpeper · Mouse-ear hawkweed in Nicholas Culpeper · Ragwort in Nicholas Culpeper · Motherwort in Nicholas Culpeper · everything Nicholas Culpeper names →
Drawing on the same sources: Grieve, Culpeper
Oak galls · Nutmeg and clove · Niter, pills of · Pilewort · the bibliography →
Nearby in the alphabet
Oil of bricks · Nettle seed (Urtica dioica) · Oil of catechumens · Nepenthe (Unidentified)
Historical description, not medical advice.
