Slippery elm has been used by Native Americans for centuries. They used the tree itself for canoes and household items, and the inner bark became a go-to remedy for all sorts of ailments: fevers, diarrhoea, constipation, urinary tract infections, wounds, sore throats, and stomach problems.

The bark is still available today as a herbal supplement. You can find it as teas, powders, lozenges, tablets, capsules, and topical preparations. But does it actually work? I went through the available clinical research to find out.

What is slippery elm bark?

Slippery elm (Ulmus rubra, also called red elm) is a deciduous tree native to eastern North America and parts of Canada. The tree can grow up to 25 metres tall and has distinctive dark brown to reddish-brown inner bark.

The “slippery” name comes from what happens when you chew the inner bark or mix it with water. It produces a mucilage, which is essentially a thick, gel-like substance made of polysaccharides. This mucilage is where the supposed medicinal properties come from.

How mucilage might work

The theory behind slippery elm is straightforward: the mucilage forms a protective coating over mucous membranes. If you have an irritated throat, the gel coats it. If your digestive tract is inflamed, the gel might soothe it. This is called a “demulcent” effect.

This mechanism makes biological sense. Other mucilage-producing plants like aloe vera and flaxseed have been studied for similar purposes. The problem is that “makes sense” doesn’t mean “has been proven to work in humans.”

Traditional versus evidence-based medicine

I should be upfront about something: slippery elm has a long history of traditional use, but traditional use doesn’t equal clinical proof. Many traditional remedies turn out to have real benefits when properly studied. Others don’t. Slippery elm falls into an awkward middle ground where there’s some preliminary research, but not enough to draw firm conclusions.

The European Medicines Agency has approved slippery elm for “traditional use” in soothing minor throat irritation and as a demulcent for the digestive tract. This isn’t the same as saying it’s been proven effective. It means there’s a history of use without reported serious harm.

What the clinical research actually shows

1. Irritable bowel syndrome (IBS)

Irritable bowel syndrome affects somewhere between 5% and 20% of the population depending on which diagnostic criteria you use and where you look. It causes recurrent abdominal pain along with changes in bowel habits, whether diarrhoea, constipation, or both. It’s the most common reason people see gastroenterologists, accounting for more than 3.5 million clinic visits annually in the United States alone.

One preliminary trial looked at 31 patients with IBS over three weeks [1]. The researchers tested two different herbal formulas containing slippery elm bark alongside other ingredients.

For constipation-predominant IBS, the herbal formula improved bowel habits and several IBS symptoms including straining, abdominal pain, bloating, and stool consistency.

For diarrhoea-predominant IBS, the results were less clear. The formula didn’t improve bowel habits overall and actually increased the frequency of bowel movements. However, it did help with some symptoms like straining, abdominal pain, and bloating.

My honest assessment: This trial has serious limitations. Thirty-one patients is tiny. The formulas contained multiple herbs, so we can’t say slippery elm specifically was responsible for any effects. And three weeks isn’t long enough to know whether benefits would persist. I wouldn’t take slippery elm for IBS based on this evidence alone.

2. Psoriasis

Psoriasis is a chronic inflammatory skin condition that causes scaly, reddish patches with distinct borders. The patches can be itchy and painful. Beyond the skin, psoriasis is linked to various other conditions. About 75% of patients have at least one comorbidity, with psoriatic arthritis and cardiovascular disease being the most common [2].

One case report described five psoriasis patients who tried a dietary improvement programme combined with saffron and slippery elm bark tea [3]. Their symptoms improved, including reductions in redness, skin thickness, flaking, and affected skin area.

My honest assessment: Five patients. No control group. No blinding. A dietary programme was involved, so any improvement could have come from the diet changes rather than the slippery elm tea. This is about as weak as evidence gets. I wouldn’t use slippery elm for psoriasis based on this.

3. Acute pharyngitis (sore throat)

Acute pharyngitis is one of the most common respiratory infections. It causes sore throat, pain when swallowing, and sometimes fever, headache, or nausea. Most cases are viral, with adenoviruses being the most common culprit. Bacterial causes, primarily Streptococcus pyogenes, account for about 30% of cases in children and somewhat less in adults.

One randomised, double-blind, placebo-controlled trial tested slippery elm bark tea in 60 patients with acute pharyngitis [4]. The trial found that the herbal tea was significantly better than placebo at temporarily relieving swallowing pain.

My honest assessment: This is the strongest evidence of the three, though “strongest” is relative. A randomised controlled trial is the right study design. The key word here is “temporarily.” Slippery elm tea might coat the throat and provide short-term relief while you drink it. Whether this is more helpful than drinking any warm liquid is unclear. But for temporary soothing of a sore throat, there’s at least some legitimate evidence.

The bottom line on benefits

I’ve been through the clinical research, and the honest summary is: there’s not much. Traditional use going back centuries means something, but it doesn’t replace proper clinical trials. If you want to try slippery elm tea for a sore throat, that seems reasonable given the one decent trial showing temporary relief. For IBS or skin conditions, the evidence is too weak to make recommendations.

Are there side effects?

Slippery elm bark has not been extensively studied for safety in clinical trials. That said, there haven’t been reports of serious adverse effects from normal use, and it has generally been considered safe when taken by mouth in reasonable amounts.

The mucilage itself is unlikely to cause problems since it’s primarily composed of carbohydrates that don’t get absorbed systemically. However, lack of reported side effects isn’t the same as proof of safety.

What we know from traditional and anecdotal reports

Some people report mild digestive symptoms like nausea or increased bowel movements. Topical application has occasionally been associated with skin irritation. These reports are scattered and not systematically documented, so their frequency is unknown.

Safety precautions (4 contraindications)

1. Pregnancy and breastfeeding

There’s no reliable safety data for slippery elm during pregnancy or breastfeeding. Some traditional sources have raised theoretical concerns about slippery elm affecting pregnancy, though these are not confirmed. Until proper safety studies exist, pregnant and nursing women should avoid it or consult their healthcare provider first [5].

2. Skin irritation risk

When applied topically, slippery elm can cause skin irritation or contact dermatitis in some people. If you’re using slippery elm externally, test a small area first and discontinue use if irritation develops.

3. Drug absorption interference

This is probably the most important practical concern. The mucilage that makes slippery elm “work” can also coat your digestive tract and potentially reduce how well other medications are absorbed. If you’re taking any oral medications, take them at least two hours apart from slippery elm supplements [6].

This applies to all oral medications, but it’s particularly relevant for drugs with narrow therapeutic windows where even small changes in absorption could matter.

4. Individual variation and quality concerns

As with any dietary supplement, responses vary between individuals. Some people may experience effects others don’t. Additionally, herbal supplements aren’t regulated as strictly as pharmaceuticals, so product quality can vary significantly between brands.

Before starting any new supplement, discuss it with your doctor or pharmacist, particularly if you have existing health conditions or take medications.

How slippery elm compares to other mucilage-producing supplements

If you’re interested in slippery elm for its demulcent properties, you might wonder how it compares to alternatives.

Chia seeds also form mucilage when wet and have been studied for digestive effects. The evidence base is similarly limited but growing.

Flaxseed contains both mucilage and omega-3 fatty acids. It has somewhat more research behind it, particularly for constipation.

Aloe vera gel also acts as a demulcent and has been studied for various conditions. The evidence quality is mixed but there’s generally more research available.

Marshmallow root (Althaea officinalis) is another traditional demulcent with similar proposed uses. Like slippery elm, it has limited modern clinical evidence.

None of these have overwhelming evidence, but if you’re looking for alternatives or want to compare options, these are in the same category.

Practical considerations

Forms available

Slippery elm bark comes in several forms. Lozenges and throat tablets are probably the most practical for sore throat relief since they dissolve slowly in the mouth. Tea or powder is mixed with water to form the mucilage directly. Capsules and tablets are swallowed whole, which may reduce the direct coating effect on the throat. You can also find topical preparations for skin application.

Dosing

There are no standardised dosing recommendations from clinical trials. Traditional doses typically range from 400mg to 2g of bark powder, taken as needed, often several times daily. For tea, the bark is usually steeped in hot water for several minutes.

What to look for when buying

Since supplement quality varies, look for products from reputable manufacturers. Third-party testing certifications can provide some assurance of quality. Avoid products with excessive additional ingredients if you want to assess slippery elm specifically.

Probiotics: 32 benefits and side effects - Another commonly used digestive supplement with more research behind it
Zinc: benefits and side effects - For immune support during illness
Vitamin C: 19 benefits and side effects - Another traditional remedy for colds and sore throats

References

Hawrelak JA, Myers SP. Effects of two natural medicine formulations on irritable bowel syndrome symptoms: a pilot study. J Altern Complement Med. 2010;16(10):1065-1071.
NHS. Psoriasis - Overview. https://www.nhs.uk/conditions/psoriasis/
Brown AC, Hairfield M, Richards DG, et al. Medical nutrition therapy as a potential complementary treatment for psoriasis—five case reports. Altern Med Rev. 2004;9(3):297-307.
Brinckmann J, Sigwart H, van Houten Taylor L. 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. J Altern Complement Med. 2003;9(2):285-298.
National Center for Complementary and Integrative Health. Using Dietary Supplements Wisely. https://www.nccih.nih.gov/health/using-dietary-supplements-wisely
Mount Sinai. Slippery Elm. https://www.mountsinai.org/health-library/herb/slippery-elm