Mu Zei

Mu Zei (Herba Equiseti Hiemalis) is the dried aerial stem of Equisetum hyemale L., a perennial evergreen herbaceous plant in the family Equisetaceae. In the traditional TCM classification system, Mu Zei is considered sweet and bitter in flavor with a neutral nature. It enters the Lung, Liver, and Gallbladder meridians, giving it a central role in formulas that address Wind-Heat patterns affecting the eyes, bleeding disorders, and sweating disorders.

Botanical description: Equisetum hyemale is a primitive, non-flowering vascular plant belonging to the division Pteridophyta (ferns and horsetails). It is a rhizomatous perennial that produces sterile and fertile stems that are similar in appearance. The stems are erect, dark green, hollow, jointed, and deeply grooved, typically reaching 30–100 cm in height and 5–8 mm in diameter. The stems have a rough, sandpaper-like texture due to the high silica content embedded in the epidermal cell walls. At each node, the stem is encircled by a sheath of fused, scale-like leaves that form a dark green or blackish band with a white or pale margin at the top. The stem tips bear a cone-like strobilus (spore-bearing structure) in fertile specimens. The plant has no true leaves, flowers, or seeds — it reproduces through spores produced in the strobilus.

Habitat and cultivation: E. hyemale is native to temperate regions across the Northern Hemisphere, including North America, Europe, and Asia. In China, it is distributed primarily in northeastern, northern, and southwestern provinces, including Heilongjiang, Jilin, Liaoning, Hebei, Shaanxi, Gansu, Sichuan, and Yunnan. The plant prefers moist, shaded environments such as stream banks, wet meadows, forest edges, and roadside ditches. It grows in colonies via underground rhizomes and can spread aggressively in suitable conditions. The stems are harvested in summer and autumn, typically between July and September, when the plant reaches its full height. After harvesting, the stems are cleaned, the leaf sheaths and sterile branches are removed, and the material is sun-dried or air-dried for medicinal use.

Quality markers: The Chinese Pharmacopoeia specifies that high-quality Mu Zei should be pale greenish-grey to greyish-green, with a hollow, jointed stem, a rough texture, and a characteristic light, earthy odor. The stems should be long, straight, thick, and uniform in color, free from mold, insect damage, or excessive fragmentation. The material is typically cut into segments of 1–2 cm in length for clinical use. Chemical markers and pharmacopoeial standards are specified for quality control of commercial Mu Zei preparations, including limits on heavy metals and pesticide residues.

In the traditional Chinese medicine theoretical framework, Mu Zei is understood in terms of its effects on specific patterns of disharmony (zheng). Because Mu Zei enters the Lung, Liver, and Gallbladder meridians and has a sweet, bitter, and neutral quality, it is traditionally indicated for a range of patterns involving Wind-Heat invasion, Liver Fire, and disorders of the upper body.

Dispersing Wind-Heat and clearing the eyes: Mu Zei is considered one of the most important herbs in TCM for treating eye disorders associated with Wind-Heat patterns. In TCM theory, when Wind-Heat invades the Liver meridian and ascends to the eyes, symptoms such as red, swollen, painful eyes, photophobia (aversion to light), excessive tearing, and blurred vision may appear. Mu Zei is traditionally used to disperse Wind-Heat from the Liver meridian and clear the eyes. It is commonly combined with Ju Hua (Chrysanthemum), Chan Tui (Cicada Slough), and Sang Ye (Mulberry Leaf) in Wind-Heat dispersing formulas for eye conditions. Its neutral nature makes it milder than some other Wind-Heat dispersing herbs, allowing it to be used for a wider range of presentations.

Stopping bleeding: Mu Zei has a traditional hemostatic (blood-stopping) action and is used in TCM for various types of bleeding disorders, including epistaxis (nosebleeds), hemoptysis (coughing up blood), hematochezia (bloody stools), and uterine bleeding. Its bitter flavor is believed to consolidate and astringe, helping to contain the blood within the vessels. In TCM theory, this action is particularly relevant when bleeding is associated with Heat in the blood or upward-rebellious Qi. Stir-fried Mu Zei is traditionally considered to have a stronger hemostatic effect than the raw form. It may be combined with herbs such as Sheng Ma and Bai Ji in hemostatic formulas.

Stopping sweating: Mu Zei is also used in TCM to address abnormal sweating patterns, particularly spontaneous sweating (daytime sweating without exertion) and night sweats. In TCM theory, sweating disorders may arise from various patterns, including Qi deficiency (failure to consolidate the surface), Yin deficiency (deficiency Heat causing nocturnal sweating), or external Wind. Mu Zei's astringent quality is believed to help consolidate the exterior and stop the leakage of sweat. Its neutral nature allows it to be used in both deficiency and excess patterns when combined with appropriate herbs. However, it is traditionally considered contraindicated in individuals with Qi deficiency presenting with excessive spontaneous sweating, as its astringent action may interfere with the underlying pattern.

Clearing Liver Fire: Mu Zei enters the Liver meridian and is traditionally used for patterns of Liver Fire ascending, which may manifest as red eyes, headache, dizziness, irritability, and a bitter taste in the mouth. By clearing Liver Fire and dispersing Wind-Heat, Mu Zei is believed to restore the normal descending and dispersing functions of the Liver. It is frequently combined with Ju Hua and Chan Tui in formulas targeting Liver Fire patterns. In TCM theory, this action is closely related to the herb's traditional use for eye conditions, as the Liver meridian opens into the eyes.

Classical literature references: The Ben Cao Gang Mu (Compendium of Materia Medica, 1596 CE) by Li Shizhen recorded Mu Zei's traditional use for "clearing the eyes, dispersing Wind-Heat, stopping bleeding, and stopping sweating." The Shen Nong Ben Cao Jing(Divine Farmer's Materia Medica Classic, circa 200 CE) classified the related species Equisetum sylvaticum as a medium-grade herb. Later TCM texts further elaborated on Mu Zei's role in treating eye disorders, bleeding conditions, and sweating abnormalities, establishing it as a distinctive herb within the Wind-Heat dispersing category.

Mu Zei contains a range of bioactive compounds that have been the subject of pharmacological investigation. The following overview summarizes the major chemical constituents identified in the aerial stems of Equisetum hyemale and what is currently known about them from published research.

Silicic acid (silicon dioxide): Silicic acid is one of the most abundant constituents in Mu Zei, accounting for a significant proportion of the plant's dry weight. The high silica content is responsible for the characteristic rough texture of the stems. In traditional usage, this silica content has been associated with tissue-strengthening properties, particularly for bones, connective tissue, skin, and hair. Some pre-clinical studies have investigated the role of bioavailable silicon from Equisetum extracts in bone metabolism and collagen synthesis. However, the clinical relevance of plant-derived silicic acid for human health remains an area of ongoing research, and definitive conclusions about therapeutic benefits cannot be drawn from the current evidence.

Flavonoids: Mu Zei contains a variety of flavonoids, including kaempferol, quercetin, and their glycosides. These compounds have been studied in pre-clinical research for their antioxidant, anti-inflammatory, and antimicrobial properties. Flavonoids are known to scavenge free radicals, chelate metal ions, and modulate cellular signaling pathways involved in inflammation. Some studies suggest that the flavonoid content of Equisetum species may contribute to their traditional use in managing inflammatory conditions. However, robust human clinical data confirming these effects from whole-herb Mu Zei preparations are lacking.

Equisetum saponins: Saponins are a class of amphiphilic glycosides found in Mu Zei that have attracted research interest for their potential cytotoxic, antimicrobial, and anti-inflammatory activities. Pre-clinical studies have reported that saponin-rich extracts of Equisetum species may exhibit in-vitro cytotoxic effects against certain cancer cell lines and antimicrobial activity against various bacterial and fungal strains. The specific saponin profile of Equisetum hyemale and its pharmacological significance in the context of whole-herb preparations is an active area of investigation.

Alkaloids and other constituents: Mu Zei contains trace amounts of alkaloids, including nicotine and palustrine (equisetine), as well as phenolic acids, phytosterols, and various other secondary metabolites. The presence of alkaloids, particularly palustrine, has raised historical concerns about potential toxicity in Equisetum species, though E. hyemale is generally considered to have lower alkaloid content than some other Equisetum species (such as E. palustre). Most research on these secondary compounds remains at the pre-clinical stage, and their specific contributions to the pharmacological profile of whole-herb Mu Zei are not fully understood.

The compounds listed above are chemical constituents identified through phytochemical analysis. Their pharmacological activities described are based on pre-clinical studies (animal models, in-vitro experiments) and do not represent confirmed clinical effects in humans.

Mu Zei is a key ingredient in several classical and commonly used TCM formulas, particularly those targeting Wind-Heat patterns affecting the eyes. Below are key formulas that feature Mu Zei as a primary or significant component, along with their traditional indications and the role Mu Zei plays in each composition.

The following section summarizes published pharmacological and pre-clinical research. Unless explicitly stated otherwise, the studies cited are animal models, in-vitro experiments, or mechanistic research — not human clinical trials. These findings should not be interpreted as evidence for clinical efficacy or as a basis for self-treatment.

Phytochemical profiling and biological activity: A comprehensive study by Minutti-Calva et al. (2025) investigated the phytochemical composition, biological performance, ADMET profiling, and toxicity predictions ofEquisetum hyemale extracts. The study identified a range of bioactive compounds, including phenolic compounds, flavonoids, and saponins, and evaluated their antioxidant, antimicrobial, and cytotoxic activities. The ADMET profiling provided preliminary predictions about the absorption, distribution, metabolism, excretion, and toxicity characteristics of the identified compounds. These findings contribute to the growing body of pre-clinical evidence on the pharmacological potential of E. hyemale. However, the study was conducted in vitro and does not provide clinical evidence for therapeutic use in humans.

Wound healing effects: Aguayo-Morales et al. (2023) investigated the effects of Equisetum hyemaleextract on wound healing in a diabetic rat model. The study reported that topical application of the extract accelerated wound closure, modulated the release of IL-10 and MCP-1 (key cytokines involved in the inflammatory and proliferative phases of wound healing), and promoted collagen synthesis. These findings provide mechanistic insights into the traditional use of Equisetum species for wound healing. However, this was an animal study, and the results may not directly translate to human wound healing. Robust clinical trials are needed to confirm any therapeutic benefit in humans.

Antitumoral potential: De Queiroz et al. (2023) studied the effects of Equisetum hyemale extracts against oral squamous cell carcinoma in vivo. The study identified new substances in the extracts and reported antitumoral effects in an animal model. The research suggested that E. hyemale extracts may contain bioactive compounds with potential anticancer activity, consistent with the plant's traditional use as an anticancer agent in some folk medicine systems. It is critical to emphasize that these findings come from an animal study and do not constitute evidence for the use of Mu Zei in treating cancer in humans.

Antioxidant and cytotoxic activity: Giordani et al. (2022) evaluated the chemical, antioxidant, and cytotoxic profiles of hydroalcoholic extracts of several native plants from Southern Brazil, includingEquisetum hyemale. The study reported that E. hyemale extracts exhibited antioxidant activity in vitro and showed cytotoxic effects against certain pathogenic fungi. The chemical analysis identified phenolic compounds and flavonoids as major contributors to the observed biological activities. While these findings are scientifically interesting, they are based on in-vitro experiments and do not establish clinical efficacy for any specific condition in humans.

Bone and tissue engineering applications: Da Costa E Silva et al. (2022) developed a bioactive composite derived fromEquisetum hyemale ashes for hard and soft tissue engineering. The study demonstrated that the silica-rich plant ash could be processed into a glass-carbon composite with potential applications in bone regeneration. Leão et al. (2025) further investigated this material in a murine maxillary bone defect model and reported enhanced local bone regeneration. These materials science studies highlight the unique silica content of E. hyemale and its potential biomedical applications. However, these are biomaterials studies, not clinical studies on the therapeutic use of the herb itself.

What the research does NOT show: Despite promising pre-clinical signals, the research on Mu Zei and its active compounds does NOT demonstrate conclusive clinical efficacy for any specific disease in humans. There is no robust evidence from large-scale, randomized, placebo-controlled clinical trials that Mu Zei can treat, cure, or prevent eye diseases, bleeding disorders, cancer, or any other medical condition. The translation from animal models and in-vitro experiments to human clinical relevance is uncertain. This page does not endorse Mu Zei as a treatment for any condition.

Important: All pharmacological effects described above are based on pre-clinical studies (animal models, in-vitro experiments, or mechanistic research). They do not constitute evidence of clinical efficacy in humans. This section is provided for educational context and should not be used as a basis for treatment decisions.

General safety profile: Mu Zei is widely used in TCM practice and is generally considered to have a favorable safety profile when used appropriately in formula combinations. However, like all herbal products, it is not free of risk. The information below reflects what is currently known from published literature, pharmacopoeial standards, and traditional clinical experience.

Qi deficiency and excessive tearing: In traditional TCM theory, Mu Zei is contraindicated in individuals with Qi deficiency — characterized by fatigue, weak digestion, shortness of breath, and a weak pulse. Its astringent and dispersing actions are considered potentially depleting in such individuals. Additionally, Mu Zei is traditionally avoided in cases of excessive tearing due to Qi deficiency (as opposed to Wind-Heat or Liver Fire), where the underlying cause is the failure of Qi to consolidate the body fluids. In such cases, using Mu Zei may theoretically worsen the condition by further dispersing the exterior rather than tonifying the Qi. Mu Zei should only be used under professional guidance with appropriate Qi-tonifying herbs when Qi deficiency coexists with Wind-Heat patterns.

Alkaloid content and toxicity concerns: Some Equisetum species, particularly Equisetum palustre (marsh horsetail), contain significant levels of alkaloids including palustrine (equisetine), which can be toxic to livestock and humans if consumed in large quantities.Equisetum hyemale is generally considered to have lower alkaloid content and is regarded as safer for medicinal use. However, the alkaloid profile ofE. hyemale has not been as extensively characterized as that ofE. palustre. The Chinese Pharmacopoeia specifies quality control standards for Mu Zei to ensure its safety for clinical use. As with any herbal product, Mu Zei should be obtained from reputable sources that adhere to pharmacopoeial quality standards.

Pregnancy and lactation: Mu Zei does not have a specific traditional contraindication during pregnancy when used in formula combinations under professional guidance. However, because of its dispersing and astringent properties, it is traditionally considered that pregnant women should use it with caution. Modern pre-clinical data on Mu Zei constituents in pregnancy are insufficient to fully establish safety. Do not use Mu Zei during pregnancy or while breastfeeding without direct supervision from a qualified healthcare professional.

Drug interactions: Clinical data on Mu Zei drug interactions in humans are very limited. The high silicic acid content of Mu Zei raises theoretical concerns about potential interference with the absorption of certain medications, particularly those that may chelate with silicon compounds. There is also theoretical potential for additive effects when combined with diuretic medications, given the traditional use of Equisetum species as diuretics. The flavonoids in Mu Zei may theoretically affect the activity of hepatic cytochrome P450 enzymes, which could alter the metabolism of drugs processed through these pathways. Clinical interaction data for whole-herb Mu Zei are insufficient to draw definitive conclusions. Consult a qualified healthcare professional before combining Mu Zei with any prescription medications.

Reported side effects: Based on available reports, side effects associated with Mu Zei are generally rare and mild when used at appropriate doses under professional guidance. Occasional reports include mild gastrointestinal discomfort (nausea, bloating, or loose stools), particularly in individuals with sensitive digestion. The high silica content may cause mild throat irritation if the powdered material is inhaled. Allergic reactions (skin rash or itching) have been reported in sensitive individuals. Any suspected adverse effects should be reported to a healthcare professional.

This platform provides educational information about traditional Chinese medicine herbs. It does not recommend, endorse, or prescribe the use of Mu Zei or any other herbal product for the treatment of any medical condition. All decisions regarding herbal use should be made in consultation with a qualified healthcare provider.