Herb Stem (茎 jīng)

Deng Xin Cao

Rush pith · 灯心草

Juncus effusus L. · Medulla Junci

Also known as: Deng Xin (灯心), Deng Cao (灯草)

Deng Xin Cao (Rush pith) plant

Images shown are for educational purposes only

Rush pith is a lightweight, gentle herb used in Chinese medicine mainly to calm the mind and promote healthy urination. It is best known for settling restlessness, easing insomnia, soothing mouth sores, and helping children who cry at night due to internal Heat. Because it is mild, it is often combined with other herbs rather than used on its own.

Category Dampness-draining herbs (利水渗湿药)
Therapeutic focus Urinary Health Sleep Support Oral and Dental Health Children's Health

TCM Properties

Temperature

Slightly Cool

Taste

Sweet (甘 gān), Bland (淡 dàn)

Channels entered

Heart, Lungs, Small Intestine

Parts used

Stem (茎 jīng)

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What This Herb Does

Every herb has a specific set of actions — here's what Deng Xin Cao does in the body, explained in both everyday and TCM terms

Therapeutic focus

In practical terms, Deng Xin Cao is primarily used to support these areas of health:

Urinary Health Sleep Support Oral and Dental Health Children's Health

TCM Actions

In TCM terminology, these are the specific therapeutic actions that Deng Xin Cao performs to restore balance in the body:

Clears Heart Fire Promotes Urination and Relieves Stranguria Promotes Quality Sleep Clears Heat and reduces swelling of the throat

How these actions work

'Clears Heart Fire' means this herb draws excess Heat away from the Heart, which in TCM governs the mind and spirit. When Heart Fire flares up, it can cause restlessness, insomnia, mouth and tongue sores, and irritability. Dēng Xīn Cǎo's light, bland nature allows it to gently guide this Heat downward and out through the urine. This is especially useful for children who cry at night due to Heart Heat, and for adults with restless sleep and a red-tipped tongue.

'Promotes urination and treats strangury' means this herb helps the body pass urine more freely when urination is scanty, painful, or difficult due to Damp-Heat accumulating in the lower body. Its bland taste gives it a natural seeping and draining quality. Because its medicinal strength is relatively mild, it is often used as a supporting herb alongside stronger diuretics like Mù Tōng or Chē Qián Zǐ rather than as a standalone treatment.

'Calms the spirit and stops night crying' refers to its traditional use for infants and small children who cry inconsolably at night. TCM attributes this to Heart Heat disturbing the child's spirit. Dēng Xīn Cǎo's ability to clear Heart Fire while being gentle enough for paediatric use makes it a classic choice for this condition.

'Clears Heat and reduces swelling of the throat' applies specifically to the charred form (Dēng Xīn Tàn). When calcined to ash and blown into the throat, it was traditionally used for acute sore throat and tonsillitis. This external application is distinct from its internal uses.

Patterns Addressed

In TCM, symptoms cluster into recognizable patterns of disharmony. Deng Xin Cao is used to help correct these specific patterns.

Why Deng Xin Cao addresses this pattern

When Heart Fire blazes upward, it disturbs the spirit and scorches the mouth and tongue. Dēng Xīn Cǎo enters the Heart channel and has a sweet, bland, slightly cool nature that gently clears Heart Fire. Crucially, its bland quality allows it to channel the Heat downward through the Small Intestine (the Heart's paired organ) and out via urination, rather than simply suppressing it. This 'guiding Heat downward and out through the urine' mechanism is the herb's signature therapeutic strategy. It is mild enough for children, making it a classic choice for paediatric Heart Fire presentations.

A practitioner would look for one or more of these signs

Insomnia

Restless sleep with a sense of heat and irritability

Mouth Ulcers

Mouth and tongue sores due to Heart Fire flaring upward

Restlessness

Mental restlessness and agitation, especially at night

Night Terrors In Children

Infant night crying caused by Heart Heat disturbing the spirit

Commonly Used For

These are conditions where Deng Xin Cao is frequently used — but only when they arise from the specific patterns it addresses, not in all cases

Arises from: Heart Fire blazing Heart Fire transmitting to the Small Intestine

TCM Interpretation

In TCM, the Heart 'houses the spirit' (shén), meaning it governs consciousness, sleep, and emotional equilibrium. When Heat or Fire accumulates in the Heart, the spirit becomes unsettled and cannot rest at night. This type of insomnia is characterised by difficulty falling asleep, a racing or restless mind, vivid dreams, a red tongue tip (the tongue area corresponding to the Heart), and often mouth or tongue sores. It differs from other insomnia patterns such as those caused by Blood Deficiency or Liver Fire in that the primary disturbance is Heat in the Heart itself.

Why Deng Xin Cao Helps

Dēng Xīn Cǎo directly enters the Heart channel and uses its cool, bland nature to clear Heart Fire without harsh bitter-cold herbs that might upset digestion. Its unique mechanism is 'guiding Heart Fire downward through the urine': by promoting urination through its action on the Small Intestine, it creates a downward pathway for Heat to exit the body, calming the spirit from above while draining Heat from below. For sleep issues, the cinnabar-coated form (Zhū Dēng Xīn) is traditionally preferred because the added cinnabar further weighs down and anchors the spirit. The herb is gentle enough for long-term use as a tea and is especially valued for children's sleep disturbances.

Also commonly used for

Night Terrors In Children

Paediatric night crying from Heart Heat

Cystitis

Bladder inflammation with Heat signs

Urethritis

Urethral inflammation with painful urination

Edema

Mild oedema where promoting urination is needed

Sore Throat

Acute sore throat, especially using the charred form externally

Jaundice

Damp-Heat type jaundice, as a supporting herb

Herb Properties

Every herb has an inherent temperature, taste, and affinity for specific channels — these properties determine how it interacts with the body

Temperature

Slightly Cool

Taste

Sweet (甘 gān), Bland (淡 dàn)

Channels Entered

Heart Lungs Small Intestine

Parts Used

Stem (茎 jīng)

Dosage & Preparation

These are general dosage guidelines for Deng Xin Cao — always follow your practitioner's recommendation, as dosages vary based on the formula and your individual condition

Standard dosage

1-3g

Maximum dosage

Up to 5g in decoction for short-term use; fresh herb may be used at 15-30g. This is a mild, light herb, so exceeding 5g of the dried pith is rarely necessary.

Dosage notes

Deng Xin Cao is a very light, mild herb and is often described as having "thin therapeutic power" (药力薄弱). For urinary conditions, it is typically used as an auxiliary herb alongside stronger diuretic herbs like Mu Tong, Hua Shi, or Che Qian Zi rather than as a standalone treatment. For calming the Heart and settling restlessness, it can be used alone as a simple tea (single-herb decoction). When processed with cinnabar (Zhu Deng Xin 朱灯心), it has enhanced calming effects and is preferred for insomnia and childhood night crying. The charred form (Deng Xin Tan 灯心炭) is used externally for throat conditions. Fresh herb is used at much higher doses (15-30g) than the dried pith.

Preparation

Due to its extremely light weight, Deng Xin Cao tends to float on the surface of decoctions. It is best wrapped in a cloth pouch (包煎) before decocting to ensure proper extraction. Alternatively, it can be added near the end of the decoction period (5-10 minutes), as prolonged boiling is not necessary for this light substance.

Processing Methods

In TCM, the same herb can be prepared in different ways to change its effects — here's how processing alters what Deng Xin Cao does

Processing method

Whole rush pith segments are placed inside a sealed clay pot and calcined (煅) at high temperature in an oxygen-deprived environment until the monitoring paper placed on the lid turns scorched yellow, then cooled completely before opening.

How it changes properties

Carbonising converts the herb from a diuretic into a hemostatic (stops bleeding) and astringent substance. The cooling and draining properties of the raw herb are largely replaced by an astringent, wound-healing quality. The charred form is primarily used externally rather than internally.

When to use this form

Used externally for acute sore throat (blown as powder into the throat), tonsillitis, and oral ulcers. Also applied topically to stop bleeding from minor wounds. Not used for the raw herb's typical indications of insomnia or urinary difficulty.

Common Herb Pairs

These ingredients are traditionally combined with Deng Xin Cao for enhanced therapeutic effect

Mu Tong
Mu Tong Mù Tōng 3-6g : Dēng Xīn Cǎo 1-2g

Both herbs clear Heart Heat and promote urination, but through complementary mechanisms. Mù Tōng is stronger at clearing Heart Fire and draining Heat through the Small Intestine, while Dēng Xīn Cǎo is lighter and gentler, guiding Heat downward with its bland, seeping nature. Together they create a more thorough clearing of Heart-Small Intestine Heat than either achieves alone.

When to use: Heart Fire transferring to the Small Intestine with mouth sores, irritability, and painful dark urination. This pair forms the core mechanism in several formulas treating Heat in the Heart-Small Intestine axis.

Dan Zhu Ye
Dan Zhu Ye 1:1 (Dàn Zhú Yè 3-6g : Dēng Xīn Cǎo 1-3g)

Dàn Zhú Yè (bland bamboo leaf) and Dēng Xīn Cǎo are both light, cool herbs that clear Heart Heat and promote urination. Their shared lightness means they act gently on the upper body while directing Heat downward. Combined, they provide a mild but effective clearing of Heart Fire that is safe for children and patients with sensitive digestion.

When to use: Mild Heart Heat with restlessness, insomnia, or paediatric night crying. Particularly useful when strong bitter-cold herbs would be too harsh, such as in small children or patients with weak Stomach Qi.

Che Qian Zi
Che Qian Zi Chē Qián Zǐ 9-15g : Dēng Xīn Cǎo 1-3g

Chē Qián Zǐ (plantain seed) is a strong diuretic that clears Heat and promotes urination, while Dēng Xīn Cǎo adds gentle Heart-clearing action. Together they address both the Bladder Damp-Heat causing urinary symptoms and any Heart Fire contributing to irritability or restlessness.

When to use: Hot strangury (rè lín) with painful, scanty urination accompanied by mental restlessness. This pair is particularly useful when urinary problems coexist with Heart Heat signs.

Comparable Ingredients

These ingredients have overlapping uses — here's how to tell them apart

Tong Cao
Deng Xin Cao vs Tong Cao

Both Tōng Cǎo (rice paper plant pith) and Dēng Xīn Cǎo are light, bland herbs that promote urination and are classified among Dampness-draining herbs. The key difference is that Dēng Xīn Cǎo has a stronger affinity for the Heart channel and is better at clearing Heart Fire and calming the spirit, making it the better choice for insomnia, night crying, and mouth sores. Tōng Cǎo has a stronger diuretic action and is also used to promote lactation, which Dēng Xīn Cǎo does not do.

Dan Zhu Ye
Deng Xin Cao vs Dan Zhu Ye

Both clear Heart Heat and promote urination, and both are light and gentle. Dàn Zhú Yè (bland bamboo leaf) is slightly stronger at clearing Heat from the Stomach and relieving thirst, so it is preferred when Heat affects both the Heart and the Stomach with pronounced thirst. Dēng Xīn Cǎo is specifically favoured for paediatric night crying and has a unique external use (charred form blown into the throat) for sore throat that Dàn Zhú Yè lacks.

Mu Tong
Deng Xin Cao vs Mu Tong

Both clear Heart Fire and promote urination through the Small Intestine. Mù Tōng is significantly stronger in both actions and is bitter and cold, making it the primary treatment herb. Dēng Xīn Cǎo is much milder and gentler, often used as a supporting ingredient or for mild cases. Mù Tōng can easily damage Yin or the Stomach with prolonged use, while Dēng Xīn Cǎo is gentle enough for long-term use as a tea.

Common Substitutes & Adulterants

Related species and common adulterations to be aware of when sourcing Deng Xin Cao

Deng Xin Cao may be confused with Long Xu Cao (龙须草, Eulaliopsis binata), a grass-like plant with similar appearance. Li Shizhen noted in the Ben Cao Gang Mu that Long Xu Cao has tighter, smaller stems with solid pith, whereas authentic Deng Xin Cao has slightly thicker stems with hollow, spongy white pith. The wild form of Juncus effusus, which has much thinner stems and very small pith that cannot be properly peeled, is sometimes sold as an inferior substitute for the cultivated product. In Sichuan, cultivated material with the outer bark removed is called "Deng Xin" (灯心), while unpeeled material is called "Deng Cao" (灯草), and the former is considered superior for medicinal use.

Educational content — always consult a qualified healthcare provider or TCM practitioner before using any herb.

Toxicity Classification

Classical Chinese pharmacopoeia toxicity rating for Deng Xin Cao

Non-toxic

Deng Xin Cao is classified as non-toxic in both classical sources and the modern Chinese Pharmacopoeia. Classical texts describe it as "甘寒无毒" (sweet, cold, non-toxic). However, the classical text De Pei Ben Cao cautions that prolonged or excessive use may cause dimness of vision (令人目暗). At standard dosage of 1-3g for appropriate indications, no toxicity concerns have been reported.

Contraindications

Situations where Deng Xin Cao should not be used or requires extra caution

Avoid

Lower Jiao deficiency-cold with urinary incontinence (下焦虚寒，小便不禁). Because Deng Xin Cao is cool in nature and promotes urination, it will worsen symptoms in people who already have weak, cold constitutions with inability to hold urine.

Avoid

Qi deficiency with urinary incontinence. The classical text Ben Cao Qiu Zhen specifically warns that those with Qi deficiency and inability to control urination should not use this herb.

Caution

Prolonged or excessive use. Classical sources note that overuse or long-term consumption can cause dimness of vision (目暗). Use only for the duration needed.

Caution

Deficiency-cold patterns without true Heat. As a cool, draining herb, it is inappropriate when there is no genuine Heat or Dampness to clear.

Special Populations

Important considerations for pregnancy, breastfeeding, and pediatric use

Pregnancy

No specific classical or modern contraindication for pregnancy has been documented. However, as a cool-natured herb that promotes urination, caution is advised during pregnancy. It should only be used when there is a clear clinical indication of Heat, and at standard low doses (1-3g), under practitioner guidance.

Breastfeeding

No specific contraindication for breastfeeding has been documented. Traditionally, charred Deng Xin Cao (灯心炭) was actually applied to the mother's nipple before nursing to calm a night-crying infant, suggesting it was considered safe in the breastfeeding context. Standard oral doses of 1-3g are unlikely to pose concerns, but use should be guided by a practitioner.

Children

Deng Xin Cao has a long traditional history of pediatric use, particularly for children with night crying due to Heart Heat (小儿夜啼). It is considered gentle and safe for infants and young children at reduced doses (typically one small bundle of a few strands, decocted, or about 1-2g). It can be given as a simple decoction or combined with Dan Zhu Ye (bland bamboo leaf). The charred form (灯心炭) was traditionally applied to the mother's nipple to calm a nursing infant. For pediatric febrile convulsions, it has been combined with Che Qian Cao (plantain herb).

Drug Interactions

If you are taking pharmaceutical medications, be aware of these potential interactions with Deng Xin Cao

No well-documented pharmaceutical drug interactions have been established for Deng Xin Cao. However, as a diuretic herb, theoretical caution is warranted when combined with pharmaceutical diuretics, as additive effects on fluid loss could occur.

The phenanthrene compounds in Juncus effusus (effusol, dehydroeffusol) have been shown to modulate GABA-A receptors. Theoretically, concurrent use with benzodiazepines, barbiturates, or other GABAergic sedatives could have additive sedative effects, though this has not been clinically documented at standard herbal doses.

One preclinical study found that dihydrophenanthrenes from Juncus effusus can inhibit renal organic anion transporters OAT1 and OAT3. These transporters are involved in the renal elimination of many drugs. This is a theoretical concern only at this stage and has not been demonstrated to be clinically significant at standard dosages.

Dietary Advice

Foods and dietary considerations when taking Deng Xin Cao

When taking Deng Xin Cao for Heart Heat patterns (insomnia, restlessness, mouth sores), avoid spicy, greasy, and overly warming foods that may generate more internal Heat. Favour cooling, bland foods such as mung beans, watermelon, cucumber, and pear. When using it for urinary conditions, ensure adequate fluid intake to support its diuretic action, but avoid excessive cold or iced beverages if there is any underlying Spleen weakness.

Botanical Description

Physical characteristics and morphology of the Deng Xin Cao source plant

Juncus effusus L. (common rush or soft rush) is a perennial herbaceous wetland plant in the rush family Juncaceae. It grows in dense, vase-shaped clumps up to about 1.2 metres tall, spreading by short, scaly rhizomes. The smooth, upright, cylindrical stems are bright green and leafless (the leaves are reduced to brown basal sheaths at the stem base). The stems are filled with a continuous, spongy white pith, which is the medicinal part used in TCM.

In summer, small yellowish-green to pale brown flowers emerge in loose clusters from the side of the stem, slightly below the tip, giving the appearance that the inflorescence grows laterally rather than at the top. The plant thrives in full sun in wet habitats such as marshes, bogs, stream margins, ditches, and wet meadows with moist or waterlogged soil. It has a wide distribution across temperate regions of Europe, Asia, Africa, and the Americas.

Sourcing & Harvesting

Where Deng Xin Cao is sourced, when it's harvested or collected, and how to assess quality

Harvesting season

Late summer to autumn. The stems are cut, sun-dried, then the outer bark is split open to extract the white pith, which is straightened and bundled into small bunches.

Primary growing regions

The primary production region and recognized dao di (道地药材) source for Deng Xin Cao is Jiangsu Province, particularly the Suzhou area, where it has been cultivated since at least the Ming Dynasty. It is also distributed along the lower Yangtze River basin and cultivated in Sichuan, Guizhou, and Fujian provinces. Shaanxi Province has been noted as a secondary source since the Song Dynasty. The herb grows wild throughout much of China but the cultivated Suzhou product is traditionally considered the highest quality.

Quality indicators

Good quality Deng Xin Cao pith is long (up to 90cm), relatively thick (0.1-0.3cm diameter), white to pale yellowish-white in colour, with fine longitudinal striations visible on the surface. It should be very light in weight, soft and slightly elastic, and easy to pull apart with a clean white cross-section. The pith should have minimal odour and a bland taste. Avoid pieces that are yellowed, dark, brittle, too thin, or damp. The best quality comes from cultivated plants (particularly from Suzhou), which produce thicker stems that can be properly peeled. Wild specimens tend to have thinner stems with smaller pith that cannot be properly extracted.

Classical Texts

Key passages from the classical Chinese medical texts that describe Deng Xin Cao and its therapeutic uses

《开宝本草》(Kai Bao Ben Cao, Song Dynasty)

Original: 灯心草，生江南泽地。丛生，茎圆，细而长直。人将为席。败席煮服更良。
Translation: Deng Xin Cao grows in the marshy lowlands of Jiangnan. It grows in clusters, with round, slender, long, straight stems. People weave it into mats. Decocting worn-out mats for drinking is even more effective.

《本草纲目》(Ben Cao Gang Mu, Li Shizhen, Ming Dynasty)

Original: 降心火，止血通气，散肿止渴。
Translation: It descends Heart fire, stops bleeding, promotes the flow of Qi, disperses swelling, and quenches thirst.

《本草衍义补遗》(Ben Cao Yan Yi Bu Yi, Zhu Danxi, Yuan Dynasty)

Original: 治急喉痹，烧灰吹之甚捷。
Translation: For acute throat obstruction (throat Wind-block), burning it to ash and blowing into the throat is remarkably effective.

《药品化义》(Yao Pin Hua Yi)

Original: 灯心，气味俱轻，轻者上浮，专入心肺；性味俱淡，淡能利窍，使上部郁热下行从小便而出。
Translation: Deng Xin Cao is light in both its Qi and flavour. Being light, it floats upward and enters the Heart and Lung specifically. Being bland, it opens the passages, causing accumulated Heat in the upper body to descend and exit through the urine.

《得配本草》(De Pei Ben Cao)

Original: 甘、淡，寒。入手少阴经气分。降心火，泻肺热，利小肠，退水。配麦冬，引心火下降。
Translation: Sweet, bland, cold. Enters the Qi level of the Hand Shaoyin (Heart) channel. Descends Heart fire, drains Lung Heat, benefits the Small Intestine, reduces water retention. Combined with Mai Dong (Ophiopogon), it guides Heart fire downward.

Historical Context

The history and evolution of Deng Xin Cao's use in Chinese medicine over the centuries

Deng Xin Cao was first recorded as a medicinal substance in the Song Dynasty text Kai Bao Ben Cao (开宝本草, 973 CE), though its use as a lamp wick material dates back much further. The name literally means "lamp wick grass" because the spongy white pith was traditionally used as the wick for oil lamps throughout southern China. The earliest known prescription using "lamp wick" (灯心) as an ingredient appears in Ge Hong's Zhou Hou Bei Ji Fang (肘后备急方) of the Jin Dynasty.

Understanding of this herb deepened over successive dynasties. Initially it was recorded simply as treating the "five types of painful urination" (五淋). By the Song and Yuan Dynasties, its applications had expanded to include treating children's night crying and throat obstruction. Li Shizhen in the Ben Cao Gang Mu clarified its botanical identity, distinguishing it from the similar Long Xu Cao (dragon whisker grass), noting that Deng Xin Cao has "slightly thicker stems with hollow white pith" whereas Long Xu Cao is "tighter and smaller with solid pith." The Song Dynasty Ben Cao Yan Yi further distinguished between "cooked grass" (蒸熟, steamed and dried) used for lamp wicks and "raw grass" (生草, naturally dried and peeled), specifying that raw grass was preferred for medicine.

A notable processed form is Zhu Deng Xin (朱灯心), where the pith is coated with cinnabar powder to enhance its Heart-calming and spirit-settling effects, particularly for childhood night crying. This processing method reflects the classical principle of using cinnabar to settle the Heart spirit.

Modern Research

5 published studies investigating the pharmacological effects or clinical outcomes of Deng Xin Cao

1

GABA(A) Receptor Modulators from the Chinese Herbal Drug Junci Medulla (In Vitro Pharmacological Study, 2012)

Singhuber J, Baburin I, Khom S, Zehl M, Urban E, Hering S, Kopp B. Planta Medica, 2012, 78(5): 455-458.

Researchers isolated two phenanthrene compounds (effusol and dehydroeffusol) from the pith of Juncus effusus using bioactivity-guided fractionation. Both compounds enhanced GABA-induced chloride currents on recombinant GABA-A receptors in a concentration-dependent manner, independent of the benzodiazepine binding site. This provides a pharmacological explanation for the traditional use of Deng Xin Cao as a calming and sleep-promoting herb in Chinese medicine.

PubMed
2

Cytotoxic and Anti-inflammatory Activities of Phenanthrenes from the Medullae of Juncus effusus L. (Preclinical Study, 2016)

Ma W, Zhang Y, Ding YY, Liu F, Li N. Archives of Pharmacal Research, 2016, 39(2): 154-160.

This phytochemical investigation isolated two new and 15 known phenanthrene compounds from Juncus effusus pith. Several compounds showed cytotoxic activity against five human cancer cell lines and anti-inflammatory effects by inhibiting nitric oxide production in LPS-stimulated macrophage cells, suggesting potential anti-inflammatory mechanisms for the herb's traditional uses.

3

Anti-inflammatory Effects of Juncus effusus Extract on LPS-stimulated RAW 264.7 Cells and Edema Models (Preclinical Study, 2015)

Korea Promotion Institute for Traditional Medicine Industry & Catholic University of Daegu. Immunopharmacology and Immunotoxicology, 2015.

The ethanol extract of Juncus effusus pith suppressed the production of inflammatory mediators (nitric oxide, prostaglandin E2, and pro-inflammatory cytokines) in LPS-stimulated macrophages and reduced ear and paw edema in mice. These results support the herb's traditional use for inflammatory conditions including sore throat and oral ulcers.

PubMed
4

Anxiolytic and Sedative Effects of Dehydroeffusol from Juncus effusus in Mice (Preclinical Study, 2011)

Wang YG, Wang YL, Zhai HF, Liao YJ, Zhang B, Huang JM. Natural Product Research, 2012, 26(13): 1234-1239.

Dehydroeffusol, a phenanthrene isolated from Juncus effusus, demonstrated anxiolytic and sedative properties in multiple behavioral tests in mice. This finding validates the traditional application of Deng Xin Cao for calming restlessness and promoting sleep.

PubMed
5

Anti-Inflammatory and Protective Effects of Juncus effusus L. Water Extract on Oral Keratinocytes (In Vitro Study, 2022)

Wada A, Murakami K, Ishikawa Y, et al. BioMed Research International, 2022, 2022: 9770899.

A water extract of Juncus effusus showed anti-inflammatory and protective effects on oral keratinocytes, suggesting a mechanism for the herb's traditional use in treating mouth sores and oral inflammation.

PubMed

Research on individual TCM herbs is growing but still limited by Western clinical trial standards. These studies provide emerging evidence and should be considered alongside practitioner expertise.