What is White Oak Bark?

White oak bark (Quercus alba) is the dried inner bark of the North American white oak tree. It is used mostly on the skin, in the mouth and in sitz baths as an astringent — something that tightens and dries soft tissue. Common traditional uses are gargles for sore throats, washes for minor weeping skin, and baths for piles (swollen veins around the back passage).

The honest verdict on evidence: human trial evidence for white oak bark is very thin, and most support comes from long European and North American folk use plus laboratory work. Long use in a tradition means a plant has a track record; it is not proof that it works.

It is not a treatment for infection, and it is not meant to be swallowed for long stretches. Short courses on the skin or in the mouth are the usual pattern.

How does White Oak Bark work?

The likely mechanism is simple chemistry rather than a drug-like action. White oak bark is very high in tannins, which bind to proteins on the surface of skin and mucous membranes (the moist linings of the mouth, throat and gut).

That binding forms a thin, tightened layer. In theory this reduces weeping, calms mild irritation and slows the loss of fluid from an inflamed surface.

Laboratory work also shows tannins can slow the growth of some bacteria and mop up free radicals (unstable molecules). Whether any of this makes a real difference in a person has not been properly tested.

What forms does White Oak Bark come in?

The most common form is cut or powdered dried bark, simmered in water to make a decoction (a strong tea made by boiling, not steeping).

You will also find liquid extracts and tinctures, capsules of powdered bark, and ready-made bath additives.

For skin and mouth use, the decoction is the traditional choice because you can control the strength. Capsules are the least traditional form and the hardest to use safely, because it is easy to swallow far more tannin than a rinse would give you.

Where it comes from:

White oak bark has a long record in North American folk medicine, where it was used as a wash for sores, a gargle and a remedy for loose bowels. Settlers borrowed it from Native American practice and merged it with European use of English oak (Quercus robur).

European herbalism has used oak bark in the same astringent role for centuries, and Germany's Commission E reviewed oak bark for baths, rinses and short internal use in the 1980s.

What does White Oak Bark help with?

• Sore throat and inflamed mouth or gums: This is the best-supported traditional use, though the support is tradition rather than trials. A cooled decoction used as a gargle or rinse feels tightening and may briefly ease soreness. Do not swallow the rinse, and see a dentist or doctor if gum pain, bleeding or a sore throat lasts more than a week.
• Piles (swollen veins around the back passage): Oak bark sitz baths are a standard folk measure in German and North American herbal practice for itching and weeping around the anus. No good human trial has tested white oak bark for this. Bleeding from the back passage always needs a doctor's opinion first, because it can have other causes.
• Minor weeping or irritated skin: Compresses of cooled oak bark decoction are traditionally used on small patches of weeping, oozing skin to dry them. Evidence is limited to tradition and laboratory findings about tannins. Do not use it on large raw areas, deep wounds or burns.
• Short-lived mild diarrhoea: Traditional use is a short internal course, no more than three or four days. Tannins may firm up stools, but this has not been shown in trials of white oak bark. Diarrhoea with blood, high fever, or lasting more than two days needs medical care, not herbs.
• Sweaty, irritated feet: Foot baths with oak bark are an old European home remedy for sweaty, sore feet. The drying effect is plausible from the tannin content. There is no trial evidence, and this is a comfort measure only.

Which foods are rich in White Oak Bark?

1. Black and green tea: a common everyday source of the same tannin family
2. Red wine and oak-barrel-aged spirits: pick up tannins from oak wood
3. Pomegranate: rich in ellagitannins, the same group found in oak bark
4. Walnuts and pecans: the skins carry tannins
5. Unripe persimmon: very high in astringent tannins

What are the side effects of White Oak Bark?

• Nausea, stomach ache or vomiting after swallowing it
• Constipation with repeated internal use
• Poor absorption of iron and of other medicines taken at the same time
• Dry mouth and a rough, puckering taste
• Skin dryness, redness or irritation from strong compresses or baths
• Allergic rash or itching in people sensitive to oak
• Loss of appetite with longer internal use

Good to know:

Used on the skin or as a rinse, side effects are uncommon and usually mild. Swallowing it causes trouble more often, because tannins irritate the stomach lining.

The bigger concerns come from large doses or long internal courses. Heavy, prolonged tannin intake has been linked in animals to kidney and liver damage, which is the main reason internal use is kept short.

How much White Oak Bark should you take?

• Recommended daily: There is no officially established dose in most countries, and products vary widely in strength. Traditional and German Commission E guidance for adults is about 3 g of dried bark a day taken by mouth, usually as a decoction. For gargles and mouth rinses, about 1 to 2 g of bark simmered in 150 ml of water is typical. For compresses, sitz baths and foot baths, about 20 g of bark per litre of water is the usual strength. Follow the label on any commercial extract, as concentrations differ. Do not give it by mouth to a child without medical advice.
• Best time of day: Rinses and gargles work well after meals and before bed. Sitz baths and foot baths suit the evening. If you take it by mouth, keep it at least two hours away from any other medicine you swallow.
• With or without food: Take it by mouth with or just after food. Tannins on an empty stomach commonly cause nausea and stomach ache.
• Time to effect: Astringent effects on the mouth or skin are felt within minutes, as a dry, tightened feeling. Any change in weeping skin or piles usually shows within a few days if it is going to help at all.
• How long to take it: Keep courses short. For diarrhoea, three to four days at most; for other internal use, no more than two to three weeks. Skin compresses and baths are usually used for two to three weeks. If nothing has improved after a few days, stop and get advice rather than continuing.