Botanical name: Quercus spp.
© Steven Foster
Parts used and where grown
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.
Oak has been used in
connection with the following conditions (refer to the individual
health concern for complete information):
Historical or traditional use (may
or may not be supported by scientific studies)
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
Active constituents
Tannins are the primary constituents of oak bark.2 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,3 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.4 Astringents such as oak may also help relieve the pain of sore throats and canker sores.
How much is usually taken?
The German Commission E monograph suggests 3/4 teaspoon (3 grams) of the bark per
day.5 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.
Are there any side effects or interactions?
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, orinfection bathing in water with
oak bark.6
Are there any drug
interactions?
Certain medicines may interact with oak. Refer to
drug interactions for a list of those medicines.
References: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. Weiss RF. Herbal Medicine. Beaconsfield, UK: Beaconsfield
Publishers Ltd., 1988, 328–9.
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. 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.
6. 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.