The inner bark of the slippery elm tree has been used as an herbal remedy in the United States for centuries. The mucilaginous texture of the bark is responsible for the medicinal properties of this plant. In fact, the mucilage is so effective in treating sore throats and coughs that the U.S. Food and Drug Administration has proclaimed slippery elm a safe and effective remedy for soothing throat and respiratory irritation. Slippery elm is an official drug of the U.S. Pharmacopoeia.

Native Americans traditionally employed slippery elm in healing salves for wounds, boils, ulcers, burns, and skin inflammation. Antiseptic poultices made from the mucilage were applied to gangrenous wounds. Legend has it that a drink made from the bark was used to treat typhoid fever. And a pinch of the powder inserted into a painful hollow tooth was said to be effective into preventing decay and discomfort.

Slippery elm is also considered a wholesome nutritional food. Because the mucilage does not dissolve but instead swells in water, it can be prepared as a gruel similar to oatmeal. Consumed three times per day, unsweetened "elm food" provides a sustaining source of nutrients for infants and invalids. It is gentle and easily assimilated, and thus well-tolerated by patients with gastritis and other forms of intestinal inflammation such as gastric catarrh, mucous colitis (inflammation of the colon), and enteritis (inflammation of the small intestine).

Today, the popularity of slippery elm continues to soar, dramatically increasing the demand for it. To further complicate matters, the wood of the slippery elm tree has no commercial value, and the trees are left to die after their bark has been harvested. Overutilization of this species has become such a problem that the National Center for the Preservation of Medicinal Herbs recently launched an effort aimed at promoting sustainable cultivation of slippery elm.

Slippery elm is a small- to medium-size tree native to North America. It can reach a height of 20 m tall and is topped by spreading branches that form an open crown. The red-brown or orange branches grow in a downward direction, and the stalkless flowers are arranged in dense, sessile-like clusters. Slippery elm is characterized by long, obovate to oblong green leaves that darken during the fall.

The bark has deep fissures, a mucilaginous texture, and a slight but distinct odor. The inner bark, or bast, is traditionally sold for medicinal purposes in long flat pieces about 2 to 3 feet long, between 1/8 to 1/16 of an inch in thickness.

Part Used/Pharmaceutical Designation

• Inner bark

Mucilage (polysaccharides) is composed of hexoses, pentoses, methylpentoses, polyuronides, and one hexosan; after hydrolysis the mucilage yields galactose, glucose, galacturonic acid, l-rhamnose, d-galactose, trace amount of fructose. It also contains 3.0% to 6.5% tannins (unspecified), starch, minerals, phytosterols, sesquiterpenes, calcium oxalate, cholesterol.

Commercial preparations are made from the inner bark and wood of slippery elm. Both finely powdered bark for mucilaginous drinks (infusions and decoctions) and coarsely powdered bark for poultices are available. Bark should be about 10 years old to ensure optimal medicinal benefits.

Traditional uses: inflammation and ulcerations of gastrointestinal tract, demulcent (soother) of alimentary canal and other inflamed areas, emollient (skin softener and soother), nutrient, antitussive (cough preventative), and dumulcent

Internal uses: gastritis, gastric and duodenal ulcers, colitis, diarrhea, esophagitis, diverticulitis, dysentery, enteritis, inflammation of the mouth and throat, diarrhea (simultaneously soothes and astringes), convalescent or digestive food

External uses: poultice to treat wounds, burns, abscesses, boils, scalds, carbuncles (boil-like clusters), inflamed wounds, abrasions, ulcers, and other skin conditions; vaginitis, hemorrhoids, anal fissures, varicose ulcers

Clinical applications: inflammation and ulcerations of gastrointestinal tract; convalescence

Only a small amount of scientific information has been published on the pharmacology of slippery elm. The demulcent and emollient properties of this plant presumably derive from mucilages, the main constituent of the bark. Mucilages are known to have beneficial effects on burns, wounds, ulcers, external and internal inflammations and irritations, diarrhea, and dysentery effects. Laboratory research has shown that mucilaginous medicinal plants are capable of decreasing local irritation in acute gastritis. In addition, mucilages from plants suppress coughing by providing a protective coating on the respiratory mucosa.

Internal use:

• Decoction (1:8) made from powdered bark, 4 to 16 ml tid; or 5 to 20 ml (1:10) taken as often as needed (can be added to juice or oatmeal)
• Capsules: 2 to 4 g tid in 500 mg capsules
• Infusions: 4 g powdered bark in 500 ml boiling water tid as nutritional supplement

External use:

Coarse powdered bark (with adequate mucilage for viscosity, or mass consistency) is mixed with boiling water for poultices.

There is inadequate information to determine the potential toxicity of slippery elm. There are no reports of toxicity and slippery elm is considered by most to be nontoxic, since none of its main constituents are known to produce adverse side effects. Although the Council of Europe lists this plant as a natural food flavoring, the Food Additives and Contaminants Committee (FACC) recommends that it not be used as a food additive.

No known side effects or health hazards have been reported for slippery elm when it is properly administered in recommended therapeutic doses.

No clinically significant interactions between slippery elm and conventional medications are known to have been reported in the literature to date.

The powdered bark is listed as a licensed product in Schedule 1, Table A in the General Sale List (GSL) in the UK. Unpowdered or whole bark has restricted regulatory status for pharmacy use only. Slippery elm is an official entry in the U.S. Pharmacopoeia, and the U.S. FDA states that slippery elm is a safe and effective throat and respiratory soother.

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Beveridge RJ, Stoddart JP, Szarek WA, Jones JK. Some structural features of the mucilage from the bark of Ulmus fulva (slippery elm mucilage). Carbohydr Res. 1969;9:429-439.

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