Whole herbsDampness-drainingJunci Medulla

Deng Xin Cao (Common Rush Pith or Herba)

A practical guide to Deng Xin Cao: what it is, how Traditional Chinese Medicine uses it, the classical formulas it appears in, and who should be careful with it.

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Last reviewed Oct 29, 2026

Quick Facts

Latin Name	Junci Medulla
Chinese Name & Pinyin	燈心草 · Deng Xin Cao
Medicinal Part	Whole herbs
The item	Deng Xin Cao is the dried stem pith of Juncus effusus. Dan Zhu Ye is not this herb. It usually goes into light decoctions or teas.
Nature and channels	Neutral, sweet, bland. Enters the Heart, Lung, and Small Intestine. Neutral sweet bland clears heart fire, promotes urination, and leaches dampness.
Pharmacopoeia line	Clears heart fire and promotes urination. Traditionally used for irritability and sleeplessness from heart fire, mouth sores, and short red burning urine.
Pattern cues	Irritability. Sleeplessness. Mouth sores. Burning urine.
In this article	Deng Xin Cao versus Dan Zhu Ye. Gentle neutral clearing versus stronger cold draining. Why the dose is tiny. Who should skip it.

What Is Deng Xin Cao?

Deng Xin Cao (灯心草; Dēng Xīn Cǎo; Latin: Junci Medulla; English: rush pith) in the current pharmacopoeia is the dried stem pith of Juncus effusus, a slender perennial rush, usually used raw or fried to charcoal. It is neutral, sweet, and bland, enters the Heart, Lung, and Small Intestine channels, and its core actions are to clear heart fire, and to promote urination and leach dampness. It usually goes into light decoctions or calming night teas. The usual amount is 1–3 g. Light and soft in texture, it needs no first or late addition; the charcoal form is reserved for bleeding formulas.

It is not Dan Zhu Ye. Lophatherum leaf is slightly cold and clears stomach heat as well, easing thirst for mouth sores and a bitter mouth; Deng Xin Cao is neutral, lighter, and gentler, suited to mild heat in slightly weaker constitutions. Spleen-stomach deficiency-cold, with cold limbs and loose stools, is a poor match. Use caution in pregnancy. Very low urine output needs a clinic first rather than self-diuresis.

It is used most often for three patterns:

Heart-fire irritability, insomnia, mouth sores, red tongue tip
Short, red urine with burning on passing
Mild restlessness after staying up late or spicy food

Neutral, sweet, and bland, it is not a nightly “fire clearing” infusion to keep brewing. Leaching when there is no heat drains the fluids and chills the spleen-stomach.

When heart fire flares, or heart fire moves down to the small intestine, irritability, mouth sores, and short burning urine are common. Deng Xin Cao is neutral, sweet, and bland. It clears upward and leaches downward, which is why it appears in Dao Chi San (Guide Out the Red Powder)–type formulas, often with Sheng Di Huang (Unprepared Rehmannia Root) to nourish the fluids and Zhu Ye (Bamboo Leaf) to guide the heat out through urine. It leaches more than it builds. A cold weak spleen-stomach, with no fire to clear, gets colder if more is added.

Deng Xin Cao is not a catch-all calm or urinary herb. In spleen-stomach deficiency-cold, with no heat pattern, or in pregnancy, using it alone is a poor match. Raw or charred, and whether it belongs in a formula, should be decided by a licensed Chinese medicine practitioner after pattern diagnosis.

Deng Xin Cao: Materia Medica Profile

Identification & Quality Standard

Junci Medulla

Botanical Origin

The dried pith of Juncus effuses L.(Juncaceae).

Production Regions

Primarily produced in the Chinese provinces of Jiangsu, Sichuan, Fujian.

Quality Requirements

Superior medicinal material is long, thick, strong, white, flexible.

Macroscopic Features

Thin cylindrical, up to 90cm long, 1~3mm diameter; externally white or pale yellowish-white. Observed with magnification, one can see raised thin longitudinal wrinkles and sponge-like thin little holes, slightly lustrous. Light and soft texture, flexible, easily broken when pulled; fractured surface is not smooth, white. faint odor.

Main Regions and Quality Identification

Traditional materia medica and industry experience value the Deng Xin Cao produced in several provinces of the lower Yangtze and coastal south, but actual quality also depends on variety, harvest time, processing, and storage. In appearance, good-quality raw Deng Xin Cao is a slender cylinder about 1–3 mm in diameter, white or pale-yellow-white on the surface, with fine longitudinal lines, light and soft in texture, elastic when pinched, and free of impurities, mold, or worm damage. The charred Deng Xin Cao Tan is black or brown-black, crisp and easy to break, with a lustrous cross-section. The common look-alikes are the stem piths of other plants of the same genus — such as Ye Deng Xin Cao — whose pith is thinner, more yellowish on the surface, less elastic, and of poorer quality than the genuine product.

Traditional Properties & Historical Lineage

Nature, Flavour & Channel Tropism

Sweet, Bland; Slightly coldHeartLungSmall Intestine

1. Records in Classic Materia Medica

Ming Yi Bie Lu: mentions that Deng Xin Cao "governs dribbling urinary distress and unsmooth urination."
Xin Xiu Ben Cao: supplements that it can "free the waterway and remove heat."
Ben Cao Gang Mu: clearly records that Deng Xin Cao "descends the heart fire, stops bleeding, frees qi, disperses swelling, and stops thirst," and also mentions that its burnt ash applied as a coating can treat breast abscesses.
De Pei Ben Cao: notes that Deng Xin Cao "with Mai Dong treats irritability; with Zhu Ye treats red, astringent urination."
Zhong Hua Ben Cao: records that it can "clear the heart, descend fire, promote urination, and treat dribbling urinary distress."

These records all revolve around Deng Xin Cao's clearing-and-draining action — no mention of tonifying or other special effects.

2. How Views of Its Nature Changed

Though the core view of physicians through the ages is consistent, subtle differences exist: some — such as the Ming physician Miao Xi Yong — stress its heart-fire-clearing, urine-promoting action, holding it fit only for patterns with heat signs, and unsuitable for those of a deficiency-cold constitution; the Qing physician Ye Tian Shi focuses on its light-clear nature, holding that it clears while not harming the lung-stomach qi, fitting slightly weaker patients; a few physicians tried pairing it with tonics, but most later physicians hold that Deng Xin Cao's clearing-and-draining leans to dispelling the evil and has no direct tonifying action — if paired with tonics, watch the dose, to avoid over-clearing affecting the upright qi.

Core Efficacies & Traditional Applications

Traditional Functions

Promotes urination, and clears heart fire.

1. First Direction: Clearing the Heart and Descending Fire

Traditional action: clear the evil heat of the heart channel, easing the discomfort of exuberant heart fire.
Typical signs: irritability with sleeplessness, mouth sores, a red tongue tip, and agitation — mostly from staying up late, overthinking, and spicy food generating heart fire internally.
Usual combinations: often paired with other clearing-draining or mind-calming herbs — such as Zhu Ye and Mai Dong to strengthen the heart-clearing, fire-descending action, or Suan Zao Ren and Bai Zi Ren to also calm the mind and help sleep.
Who should not self-use: those with spleen-stomach cold deficiency — often cold hands and feet and loose stool — may have the internal cold worsened by Deng Xin Cao alone, causing spleen-stomach discomfort — so self-taking is not advised.

2. Second Direction: Promoting Urination and Treating Dribbling Urinary Distress

Traditional action: free the lower-burner waterway, promote urine excretion, and ease the discomfort of unsmooth urination.
Typical signs: short, red urine, a burning painful sensation on urination, and turbid urine — mostly from lower-burner damp-heat or heart fire moving down to the small intestine.
Usual combinations: often paired with other urine-promoting, dribbling-treating herbs — such as Che Qian Zi and Hua Shi to strengthen the diuretic action, or Zhi Zi and Huang Bai to also clear damp-heat.
Who should not self-use: those with abnormal kidney function, or very low urine output (less than 400 ml per day), must consult a physician first — do not self-use Deng Xin Cao to promote urination, to avoid adding burden to the body.

3. Classic Pairing: Deng Xin Cao With Che Qian Zi

Deng Xin Cao and Che Qian Zi form a common pair. Che Qian Zi itself has the actions of promoting urination, treating dribbling urinary distress, and permeating dampness to stop diarrhea — freeing the lower-burner damp-heat; Deng Xin Cao leans to clearing the heart fire and guiding it down to the small intestine, to be drained out through the urine. Combined, the pair both clears the heart fire and promotes urination, coordinating with each other — fitting the patterns of heart fire moving down to the small intestine: irritability with short, red, burning urination. Note: this pairing needs the physician's pattern diagnosis — those of a deficiency-cold constitution or without heat signs are not fit, to avoid over-clearing harming the upright qi.

Modern Research

Modern research offers useful context, but Traditional Chinese Medicine prescribes on whole-pattern diagnosis rather than isolated compounds.

1. Main Chemical Constituents

Modern research shows that the main chemical constituents detected in Deng Xin Cao include flavonoids, triterpenoids, volatile oils, and polysaccharides. Among them, flavonoid constituents such as luteolin glucoside and apigenin are naturally occurring compounds in the plant. In in vitro experiments, some flavonoid constituents show a certain inhibitory effect on the growth of some bacteria; in animal experiments, the water extract of Deng Xin Cao shows a certain diuretic action, increasing the urine volume and urinary electrolyte excretion of mice. Currently, no sufficient human clinical research confirms the specific actions of these constituents in the human body.

2. Current Research Directions

Current research on Deng Xin Cao mainly focuses on two directions:

Its diuretic action — in animal experiments, the extract of Deng Xin Cao promotes urine production, possibly related to regulating the water-salt metabolism of the kidneys.
Its anti-inflammatory action — in in vitro experiments, some constituents of Deng Xin Cao inhibit the release of inflammatory factors — but this research is still at the basic stage, and more human studies are needed to verify its actual effect in the human body.

In addition, a small amount of research looks at the antioxidant action of Deng Xin Cao, but no clear clinical application direction has formed.

3. Limitations of Current Research

Lab results are not clinical efficacy — in vitro and animal results cannot be directly equated with the same effect after a person takes Deng Xin Cao.
Extracts and monomers are not the same as traditional slices — experiments use high-concentration extracts or single constituents, while daily use is the processed slices — the dose and mode of action differ greatly.
Doses and preparation methods vary between studies — some studies use organic-solvent extracts, some use water extracts — the results may differ and no unified conclusion can form.
A single component does not define the whole herb — Deng Xin Cao works through many constituents together; research on a single constituent cannot fully explain the whole herb's mechanism.

Comparing Similar Herbs

1. What They Share

Choosing Dan Zhu Ye as the similar herb, the two share three main points:

Both have the main clearing-and-draining actions — clearing the heart fire and promoting urination.
Both are used for the traditional patterns of heart-fire exuberance with unsmooth urination — such as irritability, mouth sores, and short, red urine.
Both need constitution and dose considered — both are gentle, but those of a deficiency-cold constitution need caution with both, to avoid over-clearing harming the upright qi.

2. The Key Differences: Deng Xin Cao vs. Dan Zhu Ye

Nature and flavors: Deng Xin Cao is neutral with sweet and light flavors, entering the heart, lung, and small-intestine channels; Dan Zhu Ye leans cold with sweet and light flavors, entering the heart, stomach, and small-intestine channels. Both are sweet-light, but Dan Zhu Ye's cold is somewhat stronger — fitting patterns with more marked heat signs — while Deng Xin Cao's neutral nature fits those of a weaker constitution or with lighter heat.
Focus: Deng Xin Cao's core strength is clearing the heart fire without consuming qi, and promoting urination without harming the fluids — leaning to the light-clear, rising heart-clearing action; Dan Zhu Ye's core strength is clearing the stomach heat and heart fire together, and also removing irritability and stopping thirst — leaning to clearing the heat evil of the middle and upper burners; besides unsmooth urination, it is also used for the stomach-heat patterns of mouth sores, swollen gums, and thirst with heavy drinking.
Qi tendency: Deng Xin Cao is light and clear in texture — its action leans to floating up and clearing-discharging, mainly regulating the heart-channel qi and guiding the heart fire downward; Dan Zhu Ye's action leans to clearing-discharging — floating up to clear the heart fire, clearing the stomach heat in the middle, and promoting urination below — a wider range of qi regulation, attending to the heat evil of the upper, middle, and lower burners.
Best fit: Deng Xin Cao's traditional indicators are mostly milder irritability and short, red urine without marked thirst — fitting lighter heat and a slightly weaker constitution; Dan Zhu Ye's indicators are more marked irritability and heavier mouth sores, possibly with thirst and swollen gums — fitting deeper heat in those without marked spleen-stomach cold deficiency.
Not suitable: Deng Xin Cao — only those of a deficiency-cold constitution need caution; Dan Zhu Ye — because its nature leans cold, besides those of a deficiency-cold constitution, those with spleen-stomach weakness and frequent abdominal pain or diarrhea also need to avoid it, to avoid worsening the internal cold.
Use scenes: Deng Xin Cao appears more in light regulation — such as daily tea, the regulation of light patterns in children, or as an auxiliary herb in formulas; Dan Zhu Ye appears more in the formulas with marked heat signs — such as oral ulcers and acute urinary tract discomfort — or as a food-therapy ingredient for clearing stomach heat.

3. One-Sentence Summary

Simply put, Deng Xin Cao leans toward light, clear, neutral heart-clearing and urine-promoting, whereas Dan Zhu Ye leans toward clearing-discharging the three burners, removing irritability, and stopping thirst. Both can be used for the light heat patterns of heart fire with unsmooth urination, but they are not interchangeable.

Classical Formulas Containing Deng Xin Cao

Dao Chi San

導赤散

Formula CategoryHeat-Clearing FormulasPrimary PatternHeart FirePrimary FunctionClear Heart fire, promote urinationRelated ConditionsFrequent Urination·Dry Mouth & Throat·Anxiety Restlessness·Insomnia

View Formula Profile Read Complete Guide

Formulas vs. Single Herbs

A formula is a whole of many herbs acting together — each herb has its own unique action, and the doses and combinations are carefully designed to attend to many mechanisms and constitution needs. A single herb cannot simply replicate a full formula's effect: Deng Xin Cao's action is limited and cannot attend to nourishing yin, strongly promoting urination, or clearing stomach heat at the same time — used alone it can only ease light heat patterns, not the more complex ones. The doses and combinations in a formula are holistic — the ratio of the herbs affects the formula's action, for example, in Dao Chi San the ratio of Mu Tong to Sheng Di Huang directly affects the diuretic and yin-nourishing effects — changing the dose changes the action. The common misunderstanding: a herb that works in a formula is thought to produce the same effect when taken alone — in fact, a formula's effect is the synergy of many herbs, and taking Deng Xin Cao alone cannot reach the formula's full effect. Do not build formulas from online articles — especially for marked discomfort, consult a physician first.

Diet & Daily Home Use

1. Home Tea

Tea — Deng Xin Cao Zhu Ye Cha (Rush-and-Bamboo-Leaf Tea): raw Deng Xin Cao 1 g, Dan Zhu Ye 2 g, Mai Dong 2 g. Rinse all with clean water, put into a cup, steep in boiling water, cover 10 minutes, and drink; it can be re-steeped until the flavor fades. Suited to the irritability, mouth sores, and short, red urine from staying up late or anxiety — fitting light daily regulation for adults of a balanced or slightly weaker constitution. Not for those with spleen-stomach cold deficiency — often cold hands and feet and loose stool; pregnant women and children need use under a physician's guidance. Suggested: 1–2 times a week, one cup each time; do not drink long-term continuously. Note: Deng Xin Cao is a medicinal slice, not an ordinary food — do not increase the dose or drink it long-term casually, to avoid discomfort.

2. Decoction and Processing Differences

The difference between the raw and the processed: the raw Deng Xin Cao leans to clearing the heart and promoting urination — fitting the regulation of light heat patterns; the charred Deng Xin Cao Tan leans to stopping bleeding — mostly used in formulas for bleeding-type patterns, such as the small bleeding of mouth sores. For home decoction, Deng Xin Cao is light and soft — no pre-boiling or bag-boiling is needed; put it in the pot with the other herbs, add proper clean water, and decoct for 10–15 minutes. Different forms cannot be converted directly — for example, 1 g of Deng Xin Cao slices cannot be converted into a certain number of milliliters of extract, nor can it be directly replaced with the charred Deng Xin Cao Tan — the actions and fitting scenes of the two differ.

3. Dosage and Course

The common dose in traditional prescriptions is 1–3 g, used in formulas. The food-therapy or daily-regulation dose is 0.5–1 g, to avoid overuse. The difference between the food-therapy and medicinal doses: the food-therapy dose is smaller and gentler, fitting light daily regulation; the medicinal dose is larger and stronger, needing the physician's pattern diagnosis. Long-term continuous use is not advised — generally do not use continuously beyond 3 days; if the symptoms do not ease, consult a physician — do not extend the use on your own. Special groups — such as pregnant women, children, and those with liver or kidney impairment — need the dose adjusted to their condition, or should simply avoid use; consult a physician or pharmacist before use.

Contraindications & Safety Warnings

1. Who Should Avoid It

Deficiency-cold constitution — those with spleen-stomach cold deficiency, frequent abdominal pain or diarrhea, and cold hands and feet carry heavy internal cold — Deng Xin Cao's clearing-draining action will worsen the cold and cause spleen-stomach discomfort.
Pregnancy and breastfeeding — sufficient safety data for these groups is currently lacking — avoid self-use.
Children and the elderly — children have delicate constitutions and the elderly have weaker spleen-stomach function — use cautiously; do not self-take.
Liver or kidney impairment — consult a physician first, to avoid adding burden to the liver and kidneys.
Allergy to Deng Xin Cao or Juncaceae plants — allergic reactions may appear after contact or taking — stop at once.
Those in special treatment — such as anticoagulant treatment or chemotherapy — consult a physician before deciding whether to use it.

2. Interactions and Diet Notes

Deng Xin Cao currently has no clear drug-interaction reports, but some clearing-and-draining herbs may interact with anticoagulants, blood-pressure medications, and glucose-lowering medications — those taking these drugs should consult a doctor or pharmacist first and not self-take Deng Xin Cao. On diet: there is no sufficient evidence of a general "food clash" between ordinary foods, but certain herbs can interact with specific drugs — those on medication should consult a doctor or pharmacist first, to avoid the drug effect being affected by food or herb combinations.

3. Adverse Reactions and Overdose Risk

Deng Xin Cao has relatively few adverse reactions, but overuse or long-term taking may cause spleen-stomach discomfort — such as abdominal pain and diarrhea — and the reaction may be more marked in those of a deficiency-cold constitution. If marked discomfort, allergy signs, persistent vomiting, breathing difficulty, altered consciousness, or rapidly worsening symptoms appear, stop at once and seek medical care. In daily use, strictly control the dose — do not increase it casually or use it long-term continuously, to avoid unnecessary risk.

Frequently Asked Questions About Deng Xin Cao

What is Dengxincao? Is it the same as Dengxin or Zhuye?

Dengxincao is the dried pith of Juncus effusus, Latin name Junci Medulla. It is a common Chinese medicine centered on clearing heart fire and promoting urination. Dengxin is a synonym. Zhuye clears heat and eliminates vexation. They cannot be used interchangeably in equal amounts. Prescribe as Dengxincao. Caution in lower jiao deficiency cold.

What are the composition and effects of Dengxincao?

Pharmacopoeial name Dengxincao, Latin Juncus effusus L. Sweet and bland in taste, slightly cold in nature, enters the Heart, Lung and Small Intestine meridians. Functions to clear heart fire and promote urination. Used for vexation and insomnia, scanty and painful urination, and mouth and tongue sores. Clears the heart and promotes urination.

How to choose between raw and processed? Can Zhuye replace it?

Pith is used raw. Zhuye emphasizes clearing heat rather than strongly promoting urination, and cannot replace it in equal amounts. Commercial products are standardized; do not adjust arbitrarily.

What is the dosage of Dengxincao? Can it be used daily as a heart-clearing tea?

Decoction, 1-3g. Modern use requires physician-determined dosage. It is not a year-round "Dengxincao tea." Lower jiao deficiency cold will be further injured by prolonged use. Vexation requires short-term, physician-determined dosage and cannot replace evaluation.

What are the contraindications of Dengxincao? Can pregnant women use it?

Not suitable for lower jiao deficiency cold or urinary incontinence. Pregnant women require physician evaluation. Stop if frequent urination or fatigue occur. Seek immediate medical care for severe mouth sores or high fever.

Can Dengxincao clear heart fire and promote urination?

It can assist vexation and insomnia, scanty and painful urination, and mouth and tongue sores. It clears heart fire and promotes urination, but is not a specific remedy for all insomnia or all mouth sores.

Can Dengxincao be taken daily as a heart-clearing or diuretic tea?

Heart fire flaring upward can be used short-term in formulas; lower jiao deficiency cold will be further injured. The idea that "Dengxincao must clear the heart" cannot replace evaluation. Clearing heart fire and promoting urination requires physician-determined formulation and dosage.

How to choose between Dengxincao, Zhuye, Cheqianzi, Fuling, and Huanglian?

Dengxincao clears heart fire and promotes urination, suited to vexation with scanty urine. Zhuye clears heat and eliminates vexation. Cheqianzi promotes urination for heat strangury. Fuling promotes urination and drains dampness. Huanglian clears heat and dries dampness. Choose Dengxincao for clearing the heart; Zhuye for eliminating vexation; Cheqianzi for relieving strangury; Fuling for draining dampness; Huanglian for draining fire. Pattern differentiation applies, but large doses of Dengxincao are contraindicated in lower jiao deficiency cold.

How is Dengxincao commonly modified? What is a representative usage?

Modifications depend on the pattern. Add Zhuye for vexation; add Huanglian for mouth sores. Specify Dengxincao; do not substitute Zhuye in equal amounts for promoting urination.

How to select and store Dengxincao?

Choose regular Chinese medicinal materials with intact white pith. Discard if moldy, damp, or abnormal in odor. Store in a dry place. Purchase "Dengxincao"; do not substitute Zhuye or Cheqianzi in equal amounts for clearing heart fire and promoting urination.

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Medical Disclaimer — This article is provided for educational purposes only and describes traditional Chinese medicine concepts. It is not medical advice, and it is not intended to diagnose, treat, cure or prevent any disease. Always consult a qualified practitioner before using any herb, particularly if you are pregnant, nursing, taking medication or managing a diagnosed condition.