Oak trees grow throughout North America. Some species of oak grow around the world, including in China and the Middle East. The bark of the oak tree is used medicinally.
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Historically, herbs known as astringents have been used to soothe the pain of canker sores. These herbs usually contain tannins that can bind up fluids and possibly relieve inflammation. They are used as a mouth rinse and then are spit out. None of these herbs has been studied in modern times. Examples of astringent herbs include agrimony, cranesbill, tormentil, oak, periwinkle, and witch hazel. Witch hazel is approved by the German Commission E for local inflammations of the mouth, presumably a condition that includes canker sores.
Tannin-containing herbs may be helpful to decrease diarrhea during acute flare-ups and have been used for this purpose in traditional medicine. A preliminary trial using isolated tannins in the course of usual drug therapy for Crohn’s disease found them to be more effective for reducing diarrhea than was no additional treatment.2 Tannin-containing herbs of potential benefit include agrimony (Agrimonia spp.), green tea, oak, witch hazel, and cranesbill. Use of such herbs should be discontinued before the diarrhea is completely resolved; otherwise the disease may be aggravated.
In laboratory experiments, a tannin in oak, known as ellagitannin, inhibited intestinal secretion,3 which may help resolve diarrhea. Oak is well regarded in Germany, where it is recommended (along with plenty of electrolyte-containing fluids) to treat mild, acute diarrhea in children.4
Topical preparations containing calendula, chickweed, or oak bark5have been used traditionally to treat people with eczema but none of these has been studied in scientific research focusing on people with eczema.
has been used historically for the treatment of various menstrual disorders, including heavy menstruation.6 This is also the case with shepherd’s purse (Capsella bursa-pastoris).7 Other herbs known as astringents (tannin-containing plants that tend to decrease discharges), such as cranesbill, periwinkle, witch hazel, and oak, were traditionally used for heavy menstruation. Human trials are lacking, so the usefulness of these herbs is unknown. Black horehound was sometimes used traditionally for heavy periods, though this approach has not been investigated by modern research.
Oak bark was used traditionally by herbalists to treat hemorrhoids, varicose veins, diarrhea, and cancer. Tannic acid derived from oak trees has a long history of application in tanning hides and making ink.1
Tannins are the primary constituents of oak bark.8 These tannins are potent astringents, akin to those found in witch hazel (Hamamelis virginiana). Tannins bind liquids, absorb toxins, and soothe inflamed tissues. The oak tannin, known as ellagitannin, inhibits intestinal secretion,9 which helps resolve diarrhea. The nonirritating, astringent nature of oak has led to its recommendation for treating mild, acute diarrhea in children (along with plenty of electrolyte-containing fluids) in Europe.10 Astringents such as oak may also help relieve the pain of sore throats and canker sores.
The German Commission E monograph suggests 3/4 teaspoon (3 grams) of the bark per day.11 For eczema, oak is applied topically by first boiling 1–2 tablespoons (15–30 grams) of the bark for fifteen minutes in 2 cups (500 ml) of water. After cooling, a cloth is dipped into the liquid and applied directly to the rash several times per day. The liquid prepared this way in the morning can be used throughout the day. Unused portions should then be discarded. Up to 5 cups (1250 ml) of this same solution can be taken each day in cases of diarrhea. Alternatively, a tincture of oak, approximately 1/2 teaspoon (2–3 ml) three times daily, can be used.
Certain medicines interact with this supplement.
Tannins are a group of unrelated chemicals that give plants an astringent taste. Herbs containing high amounts of tannins may interfere with the absorption of ephedrine or pseudoephedrine taken by mouth.12 Herbs containing high levels of tannins include green tea, black tea, uva ursi (Arctostaphylos uva-ursi), black walnut (Juglans nigra),red raspberry (Rubus idaeus), oak (Quercus spp.), and witch hazel (Hamamelis virginiana).
Except for the occasional upset stomach or constipation reported after drinking the tea, oak bark is rarely associated with side effects. There are no known reasons to avoid oak during pregnancy or breast-feeding, though oak can cause constipation. It is safe for use in children and infants. The German Commission E monograph warns against people with open sores, wounds, high fever, or infection bathing in water with oak bark.13
1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Foods, Drugs, and Cosmetics, 2d ed. New York: John Wiley & Sons, 1996, 485–7.
2. Plein K, Burkard G, Hotz J. Treatment of chronic diarrhea in Crohn disease. A pilot study of the clinical effect of tannin albuminate and ethacridine lactate. Fortschr Med 1993;111:114–8 [in German].
3. Konig M, Scholz E, Hartmann R, et al. Ellagitannins and complex tannins from Quercus petraea bark. J Nat Prod 1994;57:1411–5.
4. Schilcher H. Phytotherapy in Paediatrics. Stuttgart, Germany: Medpharm Scientific Publishers, 1997, 49–50.
5. Weiss RF. Herbal Medicine. Gothenberg, Sweden: Ab Arcanum and Beaconsfield: Beaconsfield Publishers Ltd, 1988, 328–9.
6. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Foods,Drugs, and Cosmetics, 2d ed. New York: John Wiley & Sons, 1996, 168–70.
7. Ellingwood F. American Materia Medica, Therapeutics and Pharmacognosy. Sandy, OR: Eclectic Medical Publications, 1919, 1998, 354.
8. Weiss RF. Herbal Medicine. Beaconsfield, UK: Beaconsfield Publishers Ltd., 1988, 328–9.
9. Konig M, Scholz E, Hartmann R, et al. Ellagitannins and complex tannins from Quercus petraea bark. J Nat Prod 1994;57:1411–5.
10. Schilcher H. Phytotherapy in Paediatrics. Stuttgart, Germany: Medpharm Scientific Publishers, 1997, 49–50.
11. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 175–6.
12. Brinker F. Interactions of pharmaceutical and botanical medicines. J Naturopathic Med 1997;7(2):14–20.
13. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 175–6.
Last Review: 02-05-2013
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