Mu Zei (Shave Grass, Scouring Rush)

Chinese Herb Actions

Chinese Herb Dosage

• What is the typical dosage of Mu Zei?

  Our record gives 3–9 g, using the aerial tips of the scouring rush. That is a conventional, moderate range for a light exterior-releasing herb — the material is bulky and low in density, and larger figures are not used in the standard literature.

  • Decoction — 3–9 g of the dried aerial stem.
  • Powder, externally — our record notes external use in powdered form; no internal dose applies to that route.
  • Part used — the aerial tips. The rhizome is not the medicinal part.

  Source: our own herb record dosage, part-used and external-use entries, cross-referenced against multiple online sources and published materia medica consensus. Reference only — not a prescription.

Chinese Herb Contraindications & Cautions

• Are there cautions for Mu Zei?

  Our record advises caution during pregnancy, in qi and blood deficiency, in depletion of body fluids, and in urinary frequency. The pattern behind these is consistent: this is a dispersing, outward-moving and drying herb, and dispersing herbs are poorly suited to anyone already depleted.

  • Pregnancy — caution per our record.
  • Qi and blood deficiency — caution per our record; an exterior-releasing herb further disperses what is already insufficient.
  • Depletion of fluids and yin deficiency — caution per our record; the drying quality works against an already dry condition.
  • Urinary frequency — caution per our record.
  • Eye symptoms need a diagnosis — our record lists cataract, pterygium and conjunctivitis among the traditional indications. Those are ophthalmological diagnoses. Sudden vision change, eye pain or visual loss is an urgent medical matter, and this page describes traditional use, not a course of action.
  • Product identity and provenance — horsetails accumulate minerals from the soil efficiently, which has quality implications; see the toxicity section.

  Source: our own herb record caution entry; general category cautions cross-referenced against multiple online sources and published materia medica consensus. Reference information, not medical advice.

Chinese Herb Toxicity & Overdose

• Is Mu Zei toxic? What is thiaminase, and does it matter?

  Mu Zei is not classed as a toxic herb in the materia medica, and our own record does not flag it as toxic. The question that deserves a straight answer is thiaminase. Equisetum species contain thiaminase, an enzyme that breaks down thiamine (vitamin B1). This is genuinely well documented — but the documentation is veterinary, and it is important to be precise about what has actually been shown and in which species.

  • What is measured — a comparative assay of thiaminase type 1 and type 2 activity across five plants found that bracken fern (Pteridium aquilinum) and Equisetum ramosissimum had considerably higher thiaminase activity and lower thiamine content than the other plants tested. That study establishes substantial thiaminase activity in a horsetail species; it did not test E. hyemale.
  • The livestock syndrome — a review of alkaloid-containing plants poisonous to cattle and horses in Europe identifies Equisetum palustre (marsh horsetail) as a significant hazard, attributing its toxicity to thiaminase together with nicotine and piperidine alkaloids. Horses are described as highly susceptible and develop thiamine deficiency presenting as weakness, rapid weak pulse, tremors, staggering and loss of coordination. Cattle show loss of appetite, wasting, reduced milk yield and diarrhoea. The same review notes that the plants’ high silicate content makes them unpalatable, so poisoning typically follows ingestion of contaminated hay rather than deliberate grazing.
  • What this does not establish — the animal cases involve large, repeated quantities of raw plant eaten as forage over time, chiefly of E. palustre, and in horses, a species particularly vulnerable to thiamine deficiency. We could not source any documented case of thiamine deficiency in a person from the medicinal use of E. hyemale at the doses in our record. Thiaminases are enzymes, and there is a general expectation that enzymes are degraded by prolonged heating such as decoction, but we could not source a study that directly tested that for this herb. The honest position is that the enzyme is real and the livestock literature is solid, while the transfer to a short course of a decocted Chinese medicinal is unproven in either direction. It is a reason for care with raw or long-term self-administered horsetail products, not a demonstrated hazard of the traditional preparation.
  • Mineral accumulation — a controlled study found E. hyemale readily absorbs and bioaccumulates lead, copper, cobalt, manganese, zinc, iron and chromium from soil, to the point that the authors proposed it as a bioindicator plant. That is a genuine sourcing concern: material grown on contaminated ground can carry what the ground contains.
  • Liver — the NIH drug-induced liver injury reference records that oral horsetail has been implicated in serum aminotransferase elevations but has not been convincingly linked to clinically apparent liver injury with jaundice. That chapter concerns E. arvense, not this species.

  Discrepancy note: the thiaminase evidence is species-scattered. Activity has been measured in E. ramosissimum, the clinical poisoning syndrome is attributed principally to E. palustre, and the human safety and hepatic literature concerns E. arvense. None of these is E. hyemale, the species in our record. Sources that speak simply of “horsetail” blur the distinction; this page keeps the species separate rather than merging them.

  Sources: PMID 2748137 (thiaminase type 1 and 2 activities and thiamine content, including Equisetum ramosissimum); PMID 26670251, PMC 4690134, DOI 10.3390/toxins7124884 (alkaloid-containing plants poisonous to cattle and horses in Europe, E. palustre thiaminase and equine thiamine deficiency); PMID 36303438, DOI 10.1080/15287394.2022.2139313 (heavy metal bioaccumulation in E. hyemale); PMID 35998247 (NIH LiverTox horsetail chapter, E. arvense). Neutral reference facts, not a safety guarantee.

Western / Biomedical Research

Chinese Herb Clinical Studies & Research

Provided as research context — a summary of published biomedical study, not a therapeutic or medical claim.

• Is there modern research on Mu Zei (Equisetum hyemale)?

  Yes, but far less than for most herbs on this site, and almost none of it addresses the traditional eye indication. The modern literature on Equisetum hyemale specifically is modest — a few dozen indexed papers — and is dominated by materials science on the plant’s silica and by preclinical pharmacology of crude extracts, largely from Latin American research groups where the species is also used traditionally. There are no clinical trials of this herb for the indications our record lists.

  • Silica and biomineralisation — the most robust body of work. Structural and analytical studies mapped the amorphous hydrated silica layer on the stem epidermis of E. hyemale, measuring up to 33% silicon by weight at the knob tips and identifying at least two distinct forms of silica, one closely associated with cell-wall polysaccharides. Related work on the genus has examined silica deposition mechanisms and the role of callose in silicification.
  • Phytochemistry — a 2025 study characterised E. hyemale extracts and reported their phytochemistry, biological performance, ADMET profiling and computational toxicity predictions. ADMET profiling and toxicity prediction are modelling exercises, not measurements in people.
  • Wound healing — a study in diabetic rats reported that horsetail extract accelerated wound closure, with changes in IL-10 and MCP-1 release and in collagen synthesis. An animal model; the traditional external use of the powdered herb is at least directionally consistent, but this does not establish clinical effect.
  • Antitumour screening — new substances isolated from E. hyemale extracts were reported to have an antitumoral effect against oral squamous cell carcinoma in vivo. Laboratory-stage work; no therapeutic conclusion follows.
  • Environmental and quality work — the heavy metal bioaccumulation study described under toxicity is arguably the most practically relevant modern finding for anyone sourcing this herb.
  • What is missing — nothing published addresses the herb’s central traditional use, dispersing wind-heat from the eyes. That indication rests on the materia medica record alone.

  Honest summary: the science on Mu Zei is genuinely interesting where it concerns silica, and thin where it concerns medicine. It is presented as context for an old and unusual plant, not as evidence of clinical benefit for any condition.

  Sources: PMID 17786413, DOI 10.1007/s00216-007-1522-6 (silica structure and content in E. hyemale); PMID 21801378, PMC 3160890, DOI 10.1186/1471-2229-11-112 (silica deposition in horsetail); PMID 30282746, PMC 6227863, DOI 10.1098/rsbl.2018.0338 (callose and silicification); PMID 41471390, PMC 12736147, DOI 10.3390/ph18121901 (phytochemistry, biological performance and ADMET profiling of E. hyemale extracts); PMID 37111271, PMC 10141616, DOI 10.3390/ph16040514 (wound healing in diabetic rats); PMID 36535330, DOI 10.1016/j.jep.2022.116043 (antitumoral effect against oral squamous cell carcinoma, preclinical); PMID 36303438 (heavy metal bioaccumulation). Research context, not a therapeutic claim.

Chinese Herb Notes

• Why is Mu Zei called scouring rush, and why is it so abrasive?

  Because the stems are genuinely coated in silica, and people used them as sandpaper. This is not folklore — it is measurable. Analytical work on Equisetum hyemale using X-ray elemental mapping, Raman microscopy and X-ray scattering found a continuous silica layer over the entire outer surface of the stem, thickening into raised knobs along the epidermal cells. The knob tips were measured at up to 33% silicon by weight, present as pure hydrated amorphous silica. The researchers concluded that the silica most likely serves a protective and biomechanical role for the plant. Horsetails are described in that literature as among the strongest accumulators of silicon of any higher land plant.

  • The English names record the use — “scouring rush” and “shave grass” both come from the practice of using dried stems to scour pots, smooth wood and polish metal and horn. It was a working abrasive long before it was a shelf item.
  • The Chinese name says the same thing — our own record translates Mu Zei as “Wood Thief.” A plant that steals away wood is a plant that abrades it. Two unrelated naming traditions arrived independently at the same observation.
  • Why it matters practically — the silica is why the herb is gritty, why grazing animals generally avoid horsetails, and why the plant is physically tough for its size.

  Is Mu Zei the same as the horsetail sold in Western herb shops?

  No — usually a different species. Mu Zei is Equisetum hyemale, the rough or Dutch scouring rush, an evergreen unbranched horsetail. The horsetail used in Western herbalism and sold as a supplement is normally Equisetum arvense, field horsetail, a softer, branched, deciduous species marketed for urinary complaints, hair and nails, and wound healing. They are relatives in the same genus, but they are not the same herb, they are not used for the same things, and most of the human safety literature published under the word “horsetail” — including the NIH drug-induced liver injury reference chapter — is explicitly about E. arvense. When reading anything about horsetail, check which species is meant.

  • E. hyemale — Mu Zei. Sweet, bitter, neutral; Liver and Lung. Eye complaints from wind-heat; bleeding from heat.
  • E. arvense — Western field horsetail. Used as a diuretic and for connective tissue and wound healing; not the Chinese medicinal.
  • E. palustre — marsh horsetail. Not a medicinal at all: it is a recognised European livestock poison (see toxicity).

  Sources: silica structure and content in E. hyemale per PMID 17786413, DOI 10.1007/s00216-007-1522-6; species distinction and E. arvense safety literature per PMID 35998247 (NIH LiverTox horsetail chapter, explicitly E. arvense); our own herb record name translation, Latin and part used; cross-referenced against multiple online sources.