Monograph
Slippery Elm
Ulmus rubra
Updated October 4, 2026
Key points
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01
A soothing mucilage
The inner bark forms a slippery gel when wet. That coating, demulcent effect is the reason it is used for sore throats; MSKCC says it may help minor cough or sore throat.
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02
Thin clinical evidence
The best trial tested a multi-herb throat tea in 60 people and was led by its maker’s researcher. Reflux and IBS claims rest on small uncontrolled studies of blends.
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03
Space it from medicines
Mucilage may slow absorption of other oral drugs. Following EMA’s advice for marshmallow root, keep slippery elm half an hour to an hour away from medicines.
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04
An at-risk tree
Dutch elm disease and elm yellows kill slippery elm, and most bark is wild-harvested. United Plant Savers lists it as At-Risk; prefer cultivated or responsibly sourced bark.
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05
Never insert whole bark
Strips of bark were once inserted into the body to try to induce abortion, causing serious harm. The UK restricts whole bark to pharmacy sale.
Slippery elm is a North American elm named for its inner bark, which turns slick and gel-like when moistened. The US Forest Service notes that the tree is most easily identified by that “slippery” inner bark. Powdered and dried, it is sold as a tea, a powder to stir into water, capsules, and throat lozenges; United Plant Savers reports that it is also used in some baby foods. The gel is mucilage, a mixture of polysaccharides, and its soothing, coating effect on irritated tissue is the whole basis of the herb’s reputation. Memorial Sloan Kettering Cancer Center (MSKCC) summarises the evidence plainly: slippery elm may help relieve minor cough or sore throat, but there is no evidence that it treats infections, cancer, or other serious conditions.
The evidence for that soothing effect is thin. The best clinical study is a 60-person trial, led by a researcher from the tea’s manufacturer, of a blended throat tea that contained slippery elm alongside licorice and marshmallow root. Claims that slippery elm heals acid reflux, irritable bowel syndrome (IBS), or inflammatory bowel disease rest on small uncontrolled studies of multi-ingredient formulas and on laboratory experiments. The same mucilage that coats the throat may also slow the absorption of medicines swallowed at the same time, so spacing doses matters.
Two further cautions set slippery elm apart. The tree itself is under pressure: Dutch elm disease and elm yellows kill it, much of the bark sold is stripped from wild trees, and United Plant Savers lists it as “At-Risk”. And in the past, strips of whole bark were inserted into the body in attempts to induce abortion, a dangerous practice that left pieces of bark lodged in women’s bladders; the UK still restricts whole bark to pharmacy sale. Nothing here is medical advice; a sore throat with high fever, difficulty swallowing or breathing, or reflux and bowel symptoms that persist or come with weight loss, bleeding, or vomiting need medical assessment rather than an herbal tea.
In this monograph
01 The plant
Botanical profile
Ulmus rubra Muhl. belongs to Ulmaceae, the elm family, and has no recognized subspecies, varieties, or forms (Fire Effects Information System). Older literature and some product labels use the synonym Ulmus fulva (United Plant Savers). Common names include red elm, gray elm, and soft elm (US Forest Service), Indian elm (MSKCC), and moose elm (United Plant Savers). The Forest Service’s Silvics of North America gives its range as southwestern Maine west to eastern North Dakota, south to central Texas, and east to northwestern Florida, with the greatest abundance in the southern Lake States and the Corn Belt of the Midwest. It grows best on moist, rich soils of lower slopes, streambanks, river terraces, and bottomlands, but also on drier limestone hillsides. It is a medium-sized, moderately fast-growing tree that may live 200 years, reaching 18.3–21.3 m (60–70 ft) on average sites and up to 41 m on the best.
The crown is broad and rather flat-topped, with the trunk dividing into wide-spreading limbs (Fire Effects Information System). The USDA plant guide describes winter buds densely covered with red-brown hairs, rough-hairy twigs, and thick, stiff, oblong to obovate leaves 10–20 cm long, pinnately veined and lopsided at the base. Small, inconspicuous flowers appear in spring before the leaves, between February and May depending on weather and location (US Forest Service), and are pollinated mainly by wind (United Plant Savers). The fruit is a flat, nearly round, one-seeded samara 1.5–2 cm across, hairy over the seed; the seeds ripen from April to June and are dispersed by wind, with good crops every two to four years once a tree is about 15 years old (US Forest Service).
The medicinal part is the inner bark. In the trade, bark is “rossed”: the rough outer bark is scraped away from fresh strips, and high-quality rossed bark is smooth, leathery, and creamy white (United Plant Savers). MSKCC describes the key constituent as mucilage made of polysaccharides built from hexose, pentose, and methylpentose sugars, which form a viscous material when mixed with water, along with tannins. A United Plant Savers review of the bark trade, citing Braun and Cohen’s evidence-based herbal guide, adds glucose, polyuronides, starches, fat, phytosterols, and minerals such as calcium, iron, and zinc, and notes that bark from trees dying of elm yellows declines in quality and can smell of wintergreen or maple syrup.
02 Lineage
History
Slippery elm was an important tree for many Native American peoples, and the USDA plant guide records a wide range of uses. The inner bark was made into cordage. The Iroquois used scraped bark, combined with other plants, for infected and swollen glands, and inner bark was used as an eyewash for sore eyes. The Menomini drank a bark tea as a physic, and the Menomini and Meskwaki used the bark as a poultice for sores. Meskwaki women drank a bark tea to ease childbirth, the Ojibwe used the bark for sore throats, and the Dakota, Omaha-Ponca, and other tribes drank a decoction as a laxative. The guide notes that Indigenous people taught some of these uses to European settlers, who took up the bark mucilage for coughs and diarrhoea (Fire Effects Information System).
Settlers also found mechanical uses for the bark’s swelling. In 1837 William A. McDowell, a physician in Fincastle, Virginia, described strips of seasoned inner bark that, dipped in tepid water, became coated in mucilage and so slippery they were hard to hold. Used as “tents”, they were pushed into the narrow openings of abscesses and wound sinuses, where they absorbed fluid and expanded, widening the opening; he also used bark bougies on urethral strictures. He wrote that elm bark tents had been recommended to him in 1819 by a colleague in Danville, Kentucky. The bark became an article of commerce, and a United Plant Savers review of American Herbal Products Association surveys found that between 78,000 and 353,000 lb of wild-harvested dried bark entered the trade each year from 1999 to 2010.
The same swelling property had a darker use. Strips of elm bark were inserted into the cervix in attempts to induce abortion. In 1939 A. H. Charles, writing in the BMJ about foreign bodies found in the bladder after attempted abortions, noted that five such cases involving elm bark had already been reported in detail, and that in each the bark had stayed undiscovered until stones formed around it and it was removed surgically. The UK’s medicines regulator still lists whole or unpowdered slippery elm bark among herbal ingredients that may be sold only in registered pharmacies, by or under the supervision of a pharmacist, under the Human Medicines Regulations 2012. In the twentieth century slippery elm also became an ingredient of Essiac, an unproven herbal cancer remedy (MSKCC).
03 Chemistry
Active compounds and how it works
Slippery elm works mainly by physical means. MSKCC explains that the polysaccharides in its mucilage form a viscous material that coats and soothes tissue, which gives it demulcent (soothing to mucous membranes), emollient (softening to skin), and cough-suppressing effects. That is a plausible explanation for short-lived relief of a scratchy throat, in the same way as other mucilage herbs such as marshmallow root, which the European Medicines Agency (EMA) accepts as a traditional demulcent for oral and throat irritation. MSKCC adds that the fibre is thought to shorten transit time through the gut, act as a bulk-forming laxative, and adsorb toxins, and that its tannins are astringent. These are proposed mechanisms rather than effects measured in controlled human studies.
Laboratory work hints at more, but only in the dish. MSKCC summarises an experiment in which slippery elm extract scavenged oxygen free radicals and reduced their release, in a dose-dependent way, from colon biopsies taken from people with active ulcerative colitis. That finding has not been followed by clinical trials showing benefit in inflammatory bowel disease. The coating effect also has a downside: EMA warns that mucilage preparations such as marshmallow root may delay the absorption of other medicines taken at the same time. No pharmacokinetic studies specific to slippery elm appear in MSKCC’s or LiverTox’s summaries, so this caution is applied by analogy with similar mucilage herbs.
04 In practice
Common uses
Sore throat is the best-supported use, and the support is modest. In a 2003 trial, Brinckmann and colleagues randomised 60 adults with acute pharyngitis to Throat Coat, a commercial tea containing slippery elm inner bark, licorice root, marshmallow root, and licorice extract, or to a placebo tea, taking 5–8 fluid ounces four to six times a day. Pain on swallowing fell more with the herbal tea, with relief significant from 5 to 30 minutes after drinking; the summed pain intensity difference was −43.8 versus −16.5, and total pain relief scored 53.6 versus 32.4. The trial was small and short, its first author worked in research and development for the tea’s manufacturer, and because the tea combined several herbs it cannot show what slippery elm contributes alone.
For cough, MSKCC notes that slippery elm is thought to soothe, but human data are lacking. United Plant Savers puts it bluntly: although the inner bark is used as something of a cure-all, studies have not proven or disproven its effectiveness for anything other than throat aches. Topical use of the powdered bark as a poultice for wounds and skin irritation is traditional, but MSKCC again finds no human data. The USDA plant guide notes that slippery elm is sold in health food stores to relieve sore throats, coughs, and other bronchial ailments, and as a laxative; those uses reflect tradition rather than trial results.
For irritable bowel syndrome, the only clinical data come from Hawrelak and Myers’s 2010 pilot study, an open-label, uncontrolled trial of two multi-herb formulas in 31 patients. In 10 people with constipation-predominant IBS, a formula of slippery elm, lactulose, oat bran, and licorice root increased bowel movement frequency by 20% and improved symptoms such as straining, bloating, and abdominal pain. In 21 people with diarrhoea-predominant or alternating IBS, a formula of bilberry, slippery elm, agrimony, and cinnamon reduced pain, bloating, and global symptoms, but the authors concluded it was not effective in improving bowel habit. Without a control group, and with slippery elm one ingredient among several, these results cannot separate a real effect from placebo response or natural fluctuation.
Slippery elm is widely recommended for acid reflux, but a 2019 review by Ahuja and Ahuja of complementary remedies for oesophageal symptoms, which included slippery elm, concluded that a substantial gap remains between anecdotal and empirical understanding of these remedies. A 2020 study by Ried and colleagues gave a seven-ingredient powder containing slippery elm, curcumin, aloe vera, guar gum, pectin, peppermint oil, and glutamine to Australian adults with digestive disorders; the 43 who completed the 16-week pre-post study reported improvements of 60–80% in symptoms including heartburn and indigestion, but there was no separate placebo group. For diarrhoea and for cancer, including as part of the Essiac formula, MSKCC finds the evidence lacking.
05 The apothecary
Preparations and traditional use
Slippery elm is sold as powdered inner bark, cut rossed bark, capsules, herbal teas (usually blends), and throat lozenges. Traditionally the dried bark has been mixed with water and applied to wounds and skin irritations, or taken by mouth for sore throat, coughs, and digestive complaints (United Plant Savers). None of the official or clinical sources reviewed here sets a standardized dose for slippery elm on its own. The two trials that used defined amounts both tested blends: the Throat Coat trial used 5–8 fluid ounces of tea four to six times daily, and the Ried study used 5 g of its multi-ingredient powder daily, then 10 g daily. These figures describe what those products delivered, not a dose of slippery elm.
Because mucilage may slow the absorption of medicines taken at the same time, a sensible precaution is borrowed from EMA’s monograph on marshmallow root, a comparable mucilage herb: do not take the product within half an hour to an hour before or after other medicines. EMA also advises that if throat symptoms last more than a week, or if breathlessness, fever, or purulent sputum develop, a doctor should be consulted. Those warnings were written for marshmallow, but the reasoning applies equally to slippery elm throat products.
Sourcing deserves attention. United Plant Savers lists slippery elm as “At-Risk”, meaning cultivated sources should be used whenever possible and wild harvest kept very limited and monitored. Its species profile advises against using wild-harvested bark at all unless it comes from naturally felled trees, and notes that herbalists have suggested marshmallow and mullein as alternatives. Its review of the bark trade explains that stripping bark all the way around a trunk (girdling) is likely to kill the tree, recommends harvesting thin vertical strips instead, and suggests preferring trees already dying of disease. In the UK, whole or unpowdered bark is a pharmacy-only product (MHRA), so most consumer products there are powders.
Safety
Before you use slippery elm
06 Caution
Side effects
Slippery elm appears to be well tolerated, though it has rarely been studied with the systematic safety monitoring that would reveal uncommon problems. LiverTox, the US National Institutes of Health database of drug-induced liver injury, describes slippery elm as generally recognized as safe and reports no evidence that it causes liver enzyme elevations or clinically apparent liver injury. Its bibliography notes that slippery elm did not appear among 778 adverse reaction reports linked to complementary medicines in a Swedish registry, nor among herbal and dietary supplement cases in the US Drug-Induced Liver Injury Network series. Hawrelak and Myers reported that both of their IBS formulas were well tolerated.
Many products sold for throat and gut symptoms contain other herbs, and those ingredients bring their own side effects. The Throat Coat tea and the constipation formula in Hawrelak’s study both contained licorice, which has well-documented cautions of its own; the diarrhoea formula contained bilberry, agrimony, and cinnamon, and the Ried powder contained seven ingredients including peppermint oil and aloe vera. When someone reacts to a slippery elm blend, the culprit may be one of these. Reading the full ingredient list matters more than the name on the front of the pack.
The serious harms on record come from misuse of whole bark, not from swallowing powdered bark. Strips of bark inserted into the cervix or urethra in attempts to induce abortion became lodged in the bladder, where in the cases Charles described they were found only after stones had formed and had to be removed surgically. No form of the bark should ever be inserted into the body. For topical use as a poultice, MSKCC notes that human data are lacking, and there are no studies of skin reactions.
07 Caution
Contraindications
Pregnancy and breastfeeding: there are no clinical safety data for slippery elm in pregnancy or breastfeeding. Traditional use by Meskwaki women to ease childbirth (USDA plant guide) is not evidence of safety. For the comparable mucilage herb marshmallow root, EMA does not recommend use in pregnancy or breastfeeding because safety has not been established, and the same caution is reasonable here. The bark’s historical use in attempted abortion was mechanical and dangerous, and anyone who is pregnant and considering ending a pregnancy, or who has bleeding, fever, or pain after any attempt, should seek medical care promptly.
Children: no paediatric studies of slippery elm were found in the sources reviewed here. United Plant Savers notes its use in some baby foods, but that is a food-ingredient use, not evidence for medicinal doses in children. Parents should check with a pharmacist or doctor before giving slippery elm products to a child, particularly one taking regular medicines, given the possible effect on absorption. Throat teas and gut formulas often combine slippery elm with licorice or other herbs whose suitability for children differs, so every ingredient on the label needs checking, not just the slippery elm.
Symptoms that need diagnosis: a sore throat with high fever, a rash, difficulty swallowing or breathing, or symptoms lasting more than a week should be assessed rather than treated with lozenges or tea. Heartburn that is frequent or persistent, or that comes with difficulty swallowing, weight loss, vomiting, or black stools, needs medical evaluation. Bowel symptoms with bleeding, weight loss, night-time diarrhoea, or a recent change in bowel habit in middle age should be investigated before anyone assumes IBS.
People who rely on medicines whose timing and absorption matter, such as those with narrow safety margins, should be particularly careful to separate slippery elm from their doses or discuss it first with a pharmacist. Anyone with a known allergy to elm or to any ingredient in a blend should avoid the product. Because no formal interaction or long-term safety studies exist, the most cautious approach is to treat slippery elm like other fibre and mucilage products: take it separately from medicines, use it for short periods, and stop and seek advice if symptoms worsen or fail to settle.
08 Caution
Drug and herb interactions
The main interaction concern is physical. Mucilage forms a gel that coats the gut, and EMA warns for marshmallow root that this may delay the absorption of medicines taken at the same time, advising a gap of half an hour to an hour. MSKCC adds that slippery elm’s fibre is thought to adsorb substances in the gut. No slippery-elm-specific interaction studies appear in MSKCC’s or LiverTox’s summaries, so the precaution is applied by analogy, but it is easy to follow: take medicines first, then wait before taking slippery elm, or take slippery elm well away from them.
Interactions from other ingredients in blended products are more likely to matter than slippery elm itself. Licorice, a common partner in throat teas and gut formulas, has known interactions of its own. LiverTox reports no evidence that slippery elm injures the liver, so it is not expected to add to the liver risk of other medicines, but that conclusion rests on an absence of reports rather than on formal studies. Anyone on regular prescription medicines should mention slippery elm to their pharmacist.
09 Questions
Frequently Asked Questions
It may give short-term relief. Its mucilage coats and soothes irritated tissue, and MSKCC says it may help relieve minor cough or sore throat. The only trial, of 60 people, tested a blended tea that also contained licorice and marshmallow root, and was led by the manufacturer’s researcher; pain on swallowing eased within 5 to 30 minutes. It does not treat the infection behind a sore throat.
It is widely recommended, but not well studied. A 2019 review of remedies for oesophageal symptoms found a substantial gap between anecdote and evidence, and the main supporting study tested a seven-ingredient powder without a placebo group. Frequent heartburn, or heartburn with difficulty swallowing, weight loss, or vomiting, needs a doctor. Note that peppermint can make reflux worse, so avoid blends that combine the two if heartburn is your problem.
The evidence is very limited. A 2010 uncontrolled pilot study found that a constipation formula containing slippery elm, lactulose, oat bran, and licorice increased bowel movement frequency in 10 people, while a diarrhoea formula eased some symptoms but did not improve bowel habit. Enteric-coated peppermint oil has far better trial evidence for IBS symptoms.
Separate them. The gel slippery elm forms may slow the absorption of medicines taken at the same time. EMA advises leaving half an hour to an hour between the similar mucilage herb marshmallow root and other medicines, and the same gap is sensible here. Check blends for licorice, which has its own interactions, and tell your pharmacist what you take.
There are no safety data for medicinal use in pregnancy or breastfeeding, so it is best avoided or discussed with a midwife or doctor first. Historically, whole bark was inserted into the body in attempts to end pregnancies, which was dangerous and caused lasting injuries. Never insert bark or any plant material into the body; anyone with bleeding, fever, or pain in pregnancy should seek care promptly.
The UK’s medicines regulator lists whole or unpowdered slippery elm bark among herbal ingredients that can be sold only in registered pharmacies, by or under the supervision of a pharmacist, under the Human Medicines Regulations 2012. Powdered bark products are not covered by that listing. Historically, strips of whole bark were misused in attempts to induce abortion.
It is not globally threatened, but it is under pressure. Dutch elm disease and elm yellows kill the trees, the herbal trade has relied on wild-harvested bark, and United Plant Savers lists slippery elm as At-Risk. Stripping bark all the way around a trunk is likely to kill the tree. Choose cultivated or responsibly sourced products, and consider alternatives that herbalists suggest, such as marshmallow root.
No long-term safety studies exist. LiverTox describes slippery elm as generally recognized as safe, with no evidence of liver injury. The bigger long-term risk is relying on it while a persistent problem goes undiagnosed. Multi-ingredient gut products may also contain herbs such as aloe vera or licorice, which have their own cautions with regular use.
10 References
Sources
These references support the history, clinical, and safety claims on this page. They are not an endorsement of any product.
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Slippery Elm
Memorial Sloan Kettering Cancer Center, About Herbs, 2022
May help minor cough or sore throat; no evidence for infections or cancer; mucilage mechanism; Essiac ingredient; in vitro colitis findings.
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LiverTox: Slippery Elm
National Institute of Diabetes and Digestive and Kidney Diseases (PubMed 38289993), 2024
Generally recognized as safe; no evidence of liver enzyme elevations or clinically apparent liver injury.
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Silvics of North America: Slippery Elm (Ulmus rubra)
US Department of Agriculture Forest Service, 1990
Cooley and Van Sambeek: range, habitat, size, lifespan, seeding; killed by Dutch elm disease and elm yellows.
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Ulmus rubra
US Department of Agriculture Forest Service, Fire Effects Information System, 1993
Coladonato: taxonomy, common names, crown form; settlers used bark mucilage for coughs and diarrhoea.
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Plant Guide: Slippery Elm, Ulmus rubra Muhl.
USDA Natural Resources Conservation Service, 2000
Anderson: Native American uses; description of buds, leaves, and samaras; susceptibility to Dutch elm disease.
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Slippery Elm in the Herbal Marketplace – Past, Present & Future
United Plant Savers, 2017
Burkhart: trade volumes 1999–2010, rossed bark, girdling, elm yellows, sustainable harvest.
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Slippery Elm (Ulmus rubra)
United Plant Savers, Species At-Risk profile, 2026
At-Risk listing; lozenges and baby foods; evidence unproven beyond throat aches; use bark from naturally felled trees only.
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European Union herbal monograph on Althaea officinalis L., radix
European Medicines Agency (EMA/HMPC/436679/2015), 2016
Marshmallow root, a comparable mucilage herb: absorption of other medicines may be delayed; separate by ½–1 hour.
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Banned and restricted herbal ingredients
Medicines and Healthcare products Regulatory Agency (GOV.UK), 2014
Whole or unpowdered slippery elm bark: sale only in registered pharmacies under a pharmacist’s supervision.
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Safety and efficacy of a traditional herbal medicine (Throat Coat) in symptomatic temporary relief of pain in patients with acute pharyngitis: a multicenter, prospective, randomized, double-blinded, placebo-controlled study
Journal of Alternative and Complementary Medicine (PubMed 12804082), 2003
Brinckmann et al.: 60 adults with pharyngitis; pain on swallowing relieved 5–30 minutes after drinking; first author from the manufacturer.
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Effects of two natural medicine formulations on irritable bowel syndrome symptoms: a pilot study
Journal of Alternative and Complementary Medicine (PubMed 20954962), 2010
Hawrelak and Myers: open-label, uncontrolled, 31 patients; constipation formula raised bowel frequency 20%.
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Herbal formula improves upper and lower gastrointestinal symptoms and gut health in Australian adults with digestive disorders
Nutrition Research (PubMed 32151878), 2020
Ried et al.: uncontrolled 16-week study of a seven-ingredient powder including slippery elm; 43 completers.
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Popular remedies for esophageal symptoms: a critical appraisal
Current Gastroenterology Reports (PubMed 31289950), 2019
Ahuja and Ahuja: substantial gap between anecdotal and empirical understanding of remedies including slippery elm.
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Elm bark in surgery: an account of the use of the bark of the slippery elm tree (Ulmus fulva), for bougies, tents, catheters, and similar purposes in surgery
Western Journal of the Medical and Physical Sciences (PubMed 38080966), 1837
McDowell: moistened inner-bark strips used as surgical tents to dilate sinuses and strictures.
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Attempted abortion: foreign bodies in bladder
British Medical Journal (PubMed 20782534), 1939
Charles: earlier reports of elm bark lodged in the bladder after attempted abortion, found after stone formation.