Educational information, not medical advice — ask your doctor or midwife.
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Wu Yi is a single herb from Chinese medicine (TCM). It is one herb, not a mixed formula. It is made from the fruit and seeds of the large-fruited elm tree (Ulmus macrocarpa).
The fruit and seeds are fermented, then pressed into a cake. Wu Yi is also called prepared elm fruit, or elm cake.
In TCM it is grouped with herbs that expel worms. Healers have used it when they think you have gut worms. They also use it for belly pain and bloating linked to "food accumulation".
It was given to children who grew thin and weak after long-term worms. It has also been put on the skin for itchy rashes and ringworm (a fungal skin infection).
The honest evidence picture is simple. Wu Yi has a long record in Chinese medicine, but almost no modern human study.
Long use shows what people have done for ages. It does not prove the herb works. Keep that in mind for everything below.
The short answer: no one has shown how Wu Yi works in people.
TCM teaches that the herb is acrid, bitter and warming. It is said to "kill worms" and break up stuck food in the gut. That is a picture drawn in TCM words, not a tested body process.
Lab work has looked at elm fruit extracts. Tests in a dish show some effect on parasites (worms and other pests) and on fungi.
What happens in a dish often does not happen in the human gut. No human study has confirmed these findings.
Wu Yi is not a shop-shelf supplement. You get it from Chinese herb pharmacies. A trained practitioner prescribes it.
Common forms: - the dried fermented cake, broken up for a decoction (a herb tea simmered in water) - ground powder, used in pills or stirred into warm water - part of old multi-herb formulas for worms and for weak digestion in children - a paste or wash put on the skin for itchy rashes
Quality varies a lot. The end product depends on how the fruit was fermented and stored.
Wu Yi shows up in early Chinese herb texts. One is the Shen Nong Ben Cao Jing. It stayed in use through later classics, such as the Ben Cao Gang Mu.
It was mostly a remedy for children and for country folk. It was given when worms were suspected. It was also given when a child was thin, bloated and not growing well.
Its standing is strong within Chinese medicine. Outside it, the herb is hardly known.
See a doctor if your belly pain is severe, keeps coming back, or lasts more than a few days. Get medical help if you have blood in your stool, black stools, a fever, or you are vomiting and cannot keep fluids down.
See a doctor promptly if a child using this herb becomes drowsy, floppy, or is losing weight, or if a rash spreads or starts to weep.
Call emergency services if you develop swelling of the face, lips or tongue, a widespread rash, or trouble breathing after taking it.
If you think you have worms, ask a doctor for a test. Proven medicines usually clear the problem in one or two doses.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Wu Yi is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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