Herb library · Herb · Quercus alba (European relatives: Q. robur, Q. petraea, Q. pubescens)
White oak bark
The tannin-rich bark of oak trees, used as an astringent wash and drink. Europe accepts oak bark for traditional use in mild diarrhea and minor mouth, skin and hemorrhoid irritation, but no clinical study in people has been done.
Traditional use
Oak bark is an astringent: the EMA describes its tannins drying oozing wounds and forming a protective layer on the skin. The European Medicines Agency accepts traditional use of European oak bark for mild diarrhea, minor inflammation of the mouth or skin, and itching and burning from hemorrhoids once a doctor has ruled out serious disease. White oak bark was the official oak bark of the old US Pharmacopeia, and King's American Dispensatory (1905) records that American physicians used its decoction mostly on the outside: as a gargle for sore throat, a wash for ulcers, and a bath for children weakened by diarrhea.
What studies show
No studies in people of this herb on its own yet. What is known of it comes from the traditions that use it.
- Insufficient
Diarrhea, mouth and skin inflammation, hemorrhoids: the EMA says there are no data from controlled clinical studies; use rests on long tradition.
Be careful of
Cautions
- PregnancyThe EMA says oak bark should not be used during pregnancy or breastfeeding.
- ConditionNot recommended for children under 12. Have hemorrhoid-like symptoms checked by a doctor first: bleeding and itching can come from more serious bowel disease.
- InteractionTaken by mouth, oak bark tannins may reduce absorption of some alkaline medicines and of iron; the EMA suggests not taking iron and oak bark together.
- AllergyPeople allergic to the beech family (Fagaceae), which includes oaks, should be cautious.
- Ask a clinicianTalk with a clinician or pharmacist before using this if you take prescription medicines, are pregnant or breastfeeding, or are giving it to a child.
From the old books
What herbals and dispensaries of the past printed. History, in their words.
“It is, however, more generally used in decoction, as an external agent, which forms an excellent gargle for relaxed uvula and sore throat, a good stimulating astringent lotion for ulcers with spongy granulations, and an astringent injection for leucorrhœa, prolapsus ani, hemorrhoids, etc.”
Sources
- Assessment report on Quercus robur L., Quercus petraea (Matt.) Liebl., Quercus pubescens Willd., cortex (EMA/HMPC) (opens in a new tab) · EMA · read September 25, 2026
- Quercus cortex (oak bark) – herbal medicinal product (opens in a new tab) · EMA · read September 25, 2026
Reviewed September 25, 2026.