What Is It?

From generation to generation, the majestic oak tree has provided shade on sunny days, timber for furniture-makers and ship-builders, and even food in times of famine. Many Native American tribes relied on its acorns for nourishment. Not surprisingly, medicinal uses for the oak tree have a long history as well. Of the hundreds of Quercus species found in the northern hemisphere, Quercus alba is most valued in North America for medicinal purposes. Europeans rely more heavily on Quercus robur and Q. petraea.

The parts of the tree used medicinally are the bark and the galls— growths that are produced by the tree's reactions to fungi and insects. (1) The most important healing component in the smooth bark and galls of the oak tree is tannin, which has astringent and mildly antiseptic qualities. The tannin is what makes oak bark so valuable for minor wounds and Inflammation, for tightening tissue, and for decreasing oozing. Tannins have antiviral, antimicrobial, anticarcinogenic, and antioxidant properties. Tannins bind with proteins in tissues and block infectious agents from entering the tissues. (2)

Health Benefits

The astringent qualities of oak bark account for Germany's Commission E recommendation of oral preparations for diarrhea and topical formulations for treating itchy patches of eczema, mouth sores, sore throat, and inflamed hemorrhoids. However, no studies are available to confirm benefit for these conditions. (3)

Interestingly, a commercial oak bark preparation (Litiax), which is only available in Europe, is used for kidney stones. According to one small 1980 study, the product acts as a diuretic (water pill), reduces pain and inflammation, and is believed to prevent the formation of new stones. (4) However, no recent reports of studies are available to confirm these findings.

The antimicrobial and antiviral properties of oak bark may be helpful in treating E. coli. Recent laboratory studies conducted in Australia of eight herbal preparations, indicate oak bark was the most effective in treating enterohemorrhagic E. coli (the dangerous kind that you hear about in the news). The species used was Quercus infectoria, which is native to the Mediterranean region. (5)  However, it has the same family and generic characteristics as Quercus alba. (9)

Specifically oak bark may help to:

Protect against the effects of metabolic syndrome. Metabolic syndrome is a group of conditions that include excess body fat around the waist and elevated blood pressure, cholesterol, and sugar levels. Taken together, these conditions increase a person's risk of heart disease, stroke, and diabetes. One source notes German researchers report regular consumption of oak bark may lower cholesterol but does not indicate the type of studies done to reach this conclusion. (6) One animal study indicates oak bark extract improved the structure and function of the liver and heart and reduced the signs of metabolic syndrome in rats fed a high-fat, high-carbohydrate diet over a twelve-week period. (7)

Facilitate wound healing. Two animal studies have evaluated the effectiveness of oak bark in healing various types of wounds. In both studies, the animals received wounds and treatments in accordance with the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC), a non-profit organization that promotes the humane treatment of animals in science. In the first study, three animals with a total of 108 wounds had their wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) bacteria. Wounds were treated twice daily for three days with oak bark ointment, silver sulfadiazine, or nothing (control wounds). Nine wounds were cultured after 24, 48, and 72 hours. The wounds treated with oak bark ointment had the lowest bacterial colonization compared to the untreated control wounds and the wounds treated with silver sulfadiazine.

In the second study, oak bark ointment was applied twice daily to second-degree burns on eight animals. The wounds were assessed daily from day seven through day ten. After each assessment, the proportion of the wounds healed was higher in the treatment group than in the control group. (8)

Forms

• dried bark
• liquid extract
• tea
• tincture

Dosage Information

A tea for diarrhea or other internal problems can be prepared by simmering approximately 1 teaspoon of the finely chopped bark in 1 cup (8 ounces) of water for a few minutes, then straining. Drink three cups a day. If the taste is not to your liking, try mixing 1 teaspoon of a liquid extract in 1/4 cup (2 ounces) of water. Drink this mixture three times a day.

Commercial bath formulations containing oak bark are available; follow the package instructions. As a home remedy, make a compress for local therapy by soaking a cloth in a tea prepared by mixing 20 grams of bark in 1 liter of water. Apply the compress to the affected area three times a day. This mixture may also be used for gargling and rinsing. For more generalized skin irritations, prepare an oak bark bath by mixing 5 grams of oak bark with 1 liter of water and add to bath water.

Guidelines for Use

Oak bark is likely safe when taken orally for 3-4 days and when applied topically for 2-3 weeks.

General Interaction

There are no known drug interactions with oak bark. Oak bark contains 8-20% tannins. Plants with more than 10% tannins can cause kidney damage and necrosis (cell death) of the liver. Therefore, oak bark should not be taken orally by anyone with kidney or liver dysfunction. Germany’s Commission E recommends avoiding full Oak bark baths by those with cardiac conditions, infectious diseases, large areas of skin damage from eczema, and hypertonia, a condition in which muscles have increased tension and reduced ability to stretch.

Possible Side Effects  

Oak bark contains a relatively large concentration of tannin (8 to 20%), which can cause gastrointestinal disturbances in sensitive individuals.  

Cautions  

Oak bark preparations have been safely used for decades. However, it is important not to take an oak bark bath or place large amounts of the preparation on skin that is severely burned or wounded, or on weeping eczema, because this could further irritate the area. Topically, oak bark should not be used longer than three weeks.  

There is insufficient evidence regarding safety of oak bark in pregnancy and lactation; therefore, it should be avoided.