Slippery elm side effects

Formal safety data on slippery elm taken by mouth is thin: the two studies that tested it in people did so inside multi-ingredient formulas, and neither was designed to catalogue side effects. What's documented is limited, but what exists doesn't point to a liver or serious safety problem.

What the studies reported

A 2010 pilot study of 31 adults described both of its slippery-elm-containing formulas as well tolerated over the treatment period, without listing specific adverse events. A 2020 study of a seven-ingredient digestive formula that included slippery elm ran for 16 weeks in 43 adults and reported broad symptom improvement, without describing adverse effects attributable to any single ingredient. Neither study was designed as a dedicated safety trial, and neither isolated slippery elm from the other ingredients around it, so "well tolerated" describes the formula, not slippery elm specifically.

Liver safety

A clinical reference on drug- and supplement-induced liver injury reviewed slippery elm and found no evidence that it raises liver enzymes or causes clinically apparent liver injury, describing slippery elm preparations as generally recognized as safe.

Allergic reactions

No published case report of an allergic reaction to swallowed slippery elm bark, powder or lozenges turned up in a search of the research for this page. That's an absence of evidence, not proof it can't happen — any plant-derived product carries some possibility of an individual allergic reaction, and a new rash, swelling or breathing difficulty after taking any supplement is a reason to stop and get medical attention.

Questions people ask

Does slippery elm cause liver damage?

No. A clinical liver-safety reference found no evidence that slippery elm raises liver enzymes or causes liver injury, and describes it as generally recognized as safe.

Is slippery elm safe for daily use?

The longest human study to test a slippery-elm-containing formula ran 16 weeks; nothing longer has been published, so there's no long-term safety data beyond that window. Within the studies that exist, the formulas were reported as well tolerated.

Can slippery elm cause bloating or gas?

Neither study reviewed for this page reported bloating or gas as a side effect — if anything, the formulas that included slippery elm were associated with less bloating and gas, not more, though that result belongs to the whole formula, not slippery elm alone.

What are the general side effects of slippery elm?

No dedicated safety trial of slippery elm alone exists, so there's no defined list of expected side effects the way there would be for a well-studied ingredient. What's available is limited to two small studies that described their multi-ingredient formulas as well tolerated, and a liver-safety review that found no evidence of harm.

Related reading: slippery elm benefits: what the research does and doesn't show and slippery elm and medications: what to check.