# Slippery elm (Ulmus rubra) *Red elm, moose elm, Indian elm, sweet elm; Ojibwe *anib*; *Ulmus rubra*, in the older books *Ulmus fulva* Michx.* **Known today as.** *Ulmus rubra*, a medium-sized deciduous elm native, LiverTox writes, to the eastern and central United States and Canada, “called slippery because of the slippery texture of the inner bark when it is chewed or mixed with water.” The inner bark is the drug. Grieve describes it in commerce as long, thin, tough, flexible strips that can be bent double without breaking, smelling of fenugreek, and records that, the wood having no commercial value, the tree was fully stripped and died. Its chief constituent is a mucilage, so abundant that a little of the powder makes a thick jelly with water. Kind: Plant > **Caution.** LiverTox records that it is designated “generally recognized as safe,” that there is no reliable data on its adverse effects, and that it has been linked to rare skin allergies; it has not been implicated in liver injury. ## What was it used for? A demulcent for the throat and the gut, a food for invalids, and a poultice. Smith records in 1932 that the Pillager Ojibwe used the slippery inner bark “for sore throat, especially when the throat is apt to be dry.” Grieve calls it one of the most valuable remedies in herbal practice: made into a gruel it was a food for infants and invalids, “tolerated by the stomach when all other foods fail,” given in gastritis, colitis, and coughs; and the coarse powder made what herbalists thought one of the best poultices for wounds, boils, ulcers, and burns. LiverTox names its present uses as a lozenge for sore throat, a pill for an upset stomach, and a cream for rashes and wounds. ## What does modern science say? No European monograph covers it, and it is not approved as therapy for any disease or condition. LiverTox, revised in 2024, explains its effects by the mucilage, which may soothe a sore or dry throat and coat irritated lining of the gullet and stomach, with tannins and resins that may add an astringent effect; but it notes that there have been no large clinical trials reporting on its adverse effects, and the searches of Europe PMC made for this entry found no trial of slippery elm alone. ## Pharmacognosy and toxicology - **mucilage**: the principal constituent, in large cells in the bast; very like that of linseed - **tannins**: with resins, which may add an astringent effect - **calcium oxalate**: as twin crystals **Mechanism.** LiverTox explains its effects by the mucilage, which may soothe a sore or dry throat and coat irritated lining of the gullet and stomach. **Standing.** There is no European monograph. Designated “generally recognized as safe” in the United States; official in the United States Pharmacopoeia in Grieve’s day. ## What lore surrounds it? Grieve reports the assertion that a pinch of the powder put into a hollow tooth stops the ache and delays decay, and warns that the powdered bark was often adulterated with damaged flour. ## What did the older authorities say? **Grieve, *A Modern Herbal* (1931).** “The Red Indians have long used this viscous inner bark to prepare a healing salve,” Grieve writes, and herbalists after them made it into poultices of every kind: with charcoal for old gangrenous wounds, with brewer’s yeast and new milk to hasten suppuration, with bran and hot vinegar for rheumatic and gouty joints. The moistened bark could be moulded into pessaries, teats, and suppositories, and it was said to keep fats from going rancid. ## Sources - Smith, H. H. (1932). *Ethnobotany of the Ojibwe Indians*, Slippery Elm. Bulletin of the Public Museum of the City of Milwaukee 4. Project Gutenberg, 49527. - Grieve, M. *A Modern Herbal*, “Elm, Slippery.” As published on botanical.com. - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “SlipperyElm.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2024. NCBI Bookshelf. - LiverTox: Clinical and Research Information on Drug-Induced Liver Injury, “SlipperyElm.” National Institute of Diabetes and Digestive and Kidney Diseases, updated 2024. NCBI Bookshelf. - Grieve, M. *A Modern Herbal*, “Elm, Slippery.” As published on botanical.com. --- *Slippery elm.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-17. The Thinking Press. https://thethinkingpress.org/materia-medica/slippery-elm Historical description, not medical advice.