The Health Benefits of Oak Bark

For Acute Diarrhea, Wounds, Eczema, and Other Skin Conditions

Oak bark herbal medicine in a scoop on a cutting board

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Oak bark (Quercus robur), also known as white oak, comes from the bark of a tree in the Fagaceae family. The bark from the oak tree is the only part that is used medicinally; oak bark is harvested from March to April. White oak bark is recognized as an herbal remedy that is generally safe, being listed on the GRAS list—meaning “Generally recognized to be safe” by the FDA. The German Commission E has approved the use of oak bark for the treatment of diarrhea, and it has been listed on the US Pharmacopoeia since 1916 for its astringent and antiseptic qualities.

Other names for oak bark include:

  • Common oak
  • Corteza de roble
  • Durmast oak
  • English oak
  • Pedunculate oak
  • Quercus sp. including alba, cortex, pedunculata, petraea, and sessiliflora
  • Sessile oak
  • Stave oak
  • Stone oak
  • Tanner's bark or Tanner's oak

Health Benefits

There are hundreds of various tree species with a common name of oak, but the genus Quercus (the Latin name for oak tree) includes deciduous trees or live oaks that are native to the northern hemisphere. In ancient folklore, the oak Quercus was known as the most sacred of all plants.

Oak bark is known to have many health-promoting properties, including up to 20% tannins. It’s been used to treat a wide range of maladies including colds and flu, eczema, varicose veins, and more.

In herbal medicine, oak bark is known for its strong astringent properties and for treating infections of the mouth, bleeding gums, acute diarrhea, skin conditions, wounds, burns, and cuts.

Other conditions that oak bark is commonly used for include:

  • Acute diarrhea
  • Pharyngitis (sore throat)
  • Mouth sores and bleeding gums
  • Colds, coughs, and bronchitis
  • Fever
  • Loss of appetite
  • Digestive disorders
  • Pain and inflammation
  • Arthritis

There is a lack of adequate human medical research studies (double-blind placebo studies) to back the claims of safety and effectiveness for treating these conditions.

Health Promoting Properties

The healing properties of oak bark thought to promote health benefits include:

  • Anodyne: A substance with painkilling properties
  • Astringent: A property that causes the constriction of cells and body tissues to help treat abrasions, bleeding, and other conditions
  • Depurative: Herbs that are considered to have purifying and detoxifying effects
  • Emmenagogue: A substance that stimulates or increases menstrual flow
  • Styptic: A substance capable of stopping bleeding when applied to a wound (commonly used in styptic pencils)

The high concentration of tannins in oak bark is thought to promote very strong astringent properties; this prompted health professionals in Germany to consider oak bark for the treatment of skin conditions such as:

  • Eczema
  • Skin irritation
  • Itchy patches of skin
  • Inflamed skin
  • Hemorrhoids
  • Infected wounds
  • Staph infections
  • Bleeding cuts or wounds
  • Herpes zoster (shingles) lesions

HCA Healthcare reports that oak bark may have cancer preventative properties, but using oak bark for cancer treatment will very likely not occur in the near future. This is because of the time that it takes to perform human studies that show enough evidence of clinical benefit and safety.

According to Whole Health Chicago, a commercial preparation of oak bark called “Litiax” is available in Europe as a diuretic (water pill) that also lowers pain and inflammation. Litiax’s diuretic effect has been used in Europe to prevent kidney stones from forming (in those who are prone to kidney stones).

However, some medical experts report that oak bark is contraindicated in people with kidney stones. HCA Healthcare reports that there is “very weak evidence (too weak to be relied upon at all),” when it comes to using oak bark to treat kidney stones. The medical research is in the preliminary stages and there is not enough data to recommend the safety or effectiveness in the use of oak bark for preventing kidney stones.

It’s best to consult with the healthcare provider before using any type of medicinal herbal preparation (including oak bark); this is particularly true for those with health conditions, including kidney stones and liver conditions.

Medical researchers are working to find out if oak bark is effective at lowering cholesterol, but there is not enough current clinical research evidence to support these claims.

How it Works

The strongest healing component in oak bark is its tannins. Tannins are a yellowish or brownish, bitter-tasting organic substance found in the bark and galls (abnormal growths found on trees, shrubs, and foliage) of many plants.

Tannins have astringent and antiseptic properties (considered useful in treating wounds and cuts). Tannins are also thought to speed up blood clotting and stabilize blood pressure and are thought to help lessen symptoms of acute (a severe condition that comes on quickly) diarrhea.

Other potentially active components of oak bark include saponins. Saponins are thought to assist in the removal of excess fats in the body, binding with the fats in the digestive tract and helping to break them down; this may help to lower the absorption rate of cholesterol.

But saponins are not very well understood in the medical research world. More research is needed to prove that saponins are capable of lowering cholesterol.

Saponins are also thought to be useful as an expectorant (an agent that helps enhance coughing up phlegm and mucus). But again, there is no definitive medical research evidence to prove this.

Studies

Preliminary studies have been conducted to determine the effectiveness of a topical (on the skin) oak bark ointment on a resistant form of staph infection, called methicillin-resistant Staphylococcus aureus, in wounds and in healing burns. 

The study results indicated that “The oak bark formulation can enhance the migration of epidermal cells to accelerate healing.” The study authors add that more studies are needed to conclusively deem oak bark as safe and effective in the treatment for burns and staph infections.

Possible Side Effects

According to RX List, oak bark can have some serious side effects, including stomach and intestinal symptoms and kidney or liver damage.

But, RX List also reports, “Oak bark might be safe for most people when taken for up to three to four days for diarrhea. Oak bark [may also] be safe for most people when applied directly to the skin for up to two to three weeks. When applied to damaged skin or when taken for longer than two to three weeks, oak bark is UNSAFE.”

Contraindications

A contraindication, in the medical world, indicates a medication, supplement or treatment that should not be taken or performed under specific circumstances. Contraindications for oak bark (when oak bark should not be taken) include:

  • Pregnancy or breastfeeding: There is not enough medical research information available to know whether oak bark is safe for pregnant mom’s or babies who are breastfeeding.
  • Cardiac (heart) conditions: Those who have heart conditions should not use oak bark.
  • Skin conditions or burns with large areas of broken or damaged skin: Those with open, weeping areas of the skin should not take oak bark baths.
  • Eczema: Oak bark could further irritate weeping areas. 
  • Hypertonia: This is a nerve condition that causes the muscles to tighten. Those with hypertonia should not take oak bark.
  • Kidney or liver conditions: Oak bark may worsen kidney and liver problems, particularly when used over a long time span.
  • Gastrointestinal (stomach and intestine) problems: The high concentration of tannins in oak bark (8% to 10%) could cause gastrointestinal disturbances in some people.

Selection, Preparation, and Storage

As with other herbal supplements, the right dosage of oak bark depends on many factors, including age, general health condition, what the herb is used for and more.

There are currently no hard facts about exactly what constitutes a safe and effective dose of oak bark. Be sure to consult with a healthcare provider or other medical professional before taking oak bark.

Always follow the package instructions, not exceeding the recommended dose.

Dosage and Preparation

According to RX List, oak bark can be made into a tea to drink for diarrhea, colds, fever, cough or bronchitis. It can also be taken as an appetite stimulant and for helping digestion.

An oak bark compress can be applied directly to the skin, or oak bark can be added to bathwater for swelling and pain.

Often used dosages for oak bark include:

  • One gram, three times per day, when taking oak bark by mouth
  • One to two tablespoons of oak bark, boiled for 20 minutes in two cups of water, applied to the skin three to five times per day (this dose is also for a tea to drink)

An oak bark tincture can be made by mixing oak bark with alcohol; the proper ratio should be used according to the package insert instructions.

According to Europa (European Medicines Agency):

  • A dry extract can be made to treat acute diarrhea using a ratio of 5.0-6.5:1 extraction solvent: ethanol 50% V/V.
  • A coated tablet with 140 mg of dry extract can be taken by mouth by adults and kids over 12 years of age four times per day for unspecified acute diarrhea.

Because absorption of oak bark in the intestinal tract is sometimes delayed, oak bark should be taken 1 hour or more before or after taking any medications or other herbal supplements.

Selection and Storage

The dried bark of young branches should be used for medicinal preparations of oak bark. The tannin (active components) content of oak bark changes (from a range of between 8% to 20%) depending on the time of year that the bark is harvested, the age of the branches and the method of preparation.

Store oak bark preparations in a cool, dry place, out of direct sunlight.

Common Questions

Is white oak poisonous?

The leaves and the acorns of the white oak tree have been known to be poisonous in animals (such as cattle and sheep) when ingested in large amounts. This is due to high levels of tannic acid, which could irritate the gastrointestinal (stomach and intestines) system and cause damage to the organs (including the kidneys and liver).

However, preparations made from the bark of the white oak tree have not been found to be toxic when taken in recommended dosages, for limited periods of time. More research is needed to definitively categorize oak bark as a safe and effective herbal supplement.

Do the tannins in oak bark have any side effects?

Yes, when large amounts are ingested, tannins can cause stomach irritation, nausea, vomiting, and even liver damage. There is also a suspicion that taking high doses of tannins on a regular basis may be associated with an increased risk of certain types of cancer, but more studies are needed to definitively report on the risk of taking tannins, particularly over an extended time span.

A Word From Verywell

Although there are some indications that oak bark may be safe and effective in the treatment of various ailments, there has not been sufficient double-blind placebo studies (the gold standard of studies) to back up many of the claims of oak bark’s health benefits. Because herbal supplements, such as oak bark, are not regulated strictly by the Food and Drug Administration (FDA) it’s important to consult with a medical professional or healthcare provider, about the safe and effective use of oak bark.

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Article Sources

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  1. WholeHealth Chicago. Oak Bark. Updated May 19, 2009.

  2. Davis SC, Mertz PM. Determining the effect of an oak bark formulation on methicillin-resistant staphylococcus aureus and wound healing in porcine wound models. Ostomy Wound Manage. 2008;54(10):16-8, 20, 22-5.

  3. Oak Bark. RX List. Last updated on June 18, 2019.

  4. RX List. Drugs A-Z. Oak Bark. RxList.com.

  5. HCA Healthcare. Oak Bark. Last Updated December 15, 2015.

  6. European Medicines Agency. Assessment report on Quercus robur L., Quercus p. Last updated November, 25, 2010. 

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