Chan Tui (Cicada Moulting / Cicada Slough, the dried shed exoskeleton of Cryptotympana pustulata after metamorphosis) occupies a unique position in the TCM exterior-releasing (jie biao) category: it is simultaneously the lightest and the most multi-directional. Where other Wind-Heat releasing herbs focus primarily on dispersing exterior Wind-Heat, Chan Tui adds three additional clinically important actions — promoting rash eruption, brightening the eyes, and settling Wind to stop spasm. Sweet, cold; enters Lung and Liver channels exclusively. Sweet moistens and nourishes; cold clears Heat; light-ascending quality disperses Wind-Heat outward. The Yao Xing Fu nine-character summary: “Chan Tui retreats Wind-Heat and brightens the eyes.”

I. Classical Records and TCM Properties

Five classical benchmarks:

• Shen Nong Ben Cao Jing: governs paediatric fright-epilepsy, nocturnal crying, limb spasm; adjusts adult epilepsy-agitation and body Heat-Cold
• Ming Yi Bie Lu: adjusts post-partum deficiency discomfort in women; relieves paediatric fright-crying, shan-disorder agitation
• Ben Cao Gang Mu: Li Shizhen records origin (collected from tree trunks); governs various Wind-Heat diseases; clears pox-rash heat-toxin; retreats eye membrane (yi); rapidly relieves skin itching
• Yao Xing Fu: “Chan Tui retreats Wind-Heat and brightens the eyes”
• Historical note: Chan Tui has been used as a drug-food dual-use item throughout Chinese history; it is referenced in the widest range of classical sources of any insect-derived TCM material

TCM properties: Sweet, cold; enters Lung and Liver channels. Sweet-cold-light-ascending — this combination produces the pharmacological character: light ascending dispersal from the Lung channel (to address Wind-Heat at the body surface), and cold-clearing entry into the Liver channel (to clear Liver-Fire and settle Liver-Wind). Because it enters only these two channels, its actions are precisely targeted: Lung channel for surface and respiratory Wind-Heat, Liver channel for eyes, Wind-settling, and Spirit-calming.

Regional origin and quality: Produced across China; Shandong, Henan, and Hebei production considered highest quality. Harvest: summer and autumn; collect intact shed exoskeletons from tree trunks; remove surface earth and debris; sun-dry.

Appearance and identification: Elliptical, slightly curved; length 3–4.5cm. Surface: pale yellow-white, semi-transparent with lustre. Head: antennae and compound eyes visible; thorax-dorsum: three longitudinal ridges visible; abdomen: segments clear and regular. Quality: delicate, brittle and easily fragmented; faint odour; mild taste. Premium standard: exoskeleton complete, clean without debris, light-bodied, translucent, no mould or earth.

Processing:

• Raw (sheng yong): net-clean and sun-dry; strongest Wind-dispersing, Heat-clearing, rash-promoting, eye-brightening, and fright-settling action; the most widely used form clinically
• Lightly stir-fried (wei chao): gentle fire moderates cold nature; reduces the risk of cold-natured damage to Spleen-Stomach Yang; preferred for constitutionally Spleen-Stomach weaker patients

II. Four Core Actions

1. Dispel Wind-Heat and relieve the exterior:
Disperses Wind-Heat from the body surface; the Lung-channel entry makes this action directed precisely at the body surface and upper respiratory tract. Addresses: Wind-Heat cold with fever, aversion to Wind, nasal congestion, sore and swollen throat, dry mouth and thirst, yellow sputum, distending head pain. Also used for Wind-Heat-induced aphonia and hoarse voice (sheng yin si ya) — a particularly distinctive indication, as the cicada’s legendary capacity to produce sound is the classical rationale for its voice-restoring action. Pairs with Jin Yin Hua, Lian Qiao, and Bo He (Yin Qiao San framework).

2. Promote rash eruption and relieve itching:
Unblocks skin and muscle-layer channels; assists incomplete measles rash eruption (delayed, difficult, dim-coloured rash); suppresses allergic skin reactions; rapidly eliminates body-wide itching. Addresses: urticaria, eczema, wind-rash recurring with persistent itch, non-rash idiopathic itch with reddening from scratching. Pairs with Ma Huang, Xing Ren, Shi Gao (Ma Xing Shi Gan Tang framework) for Wind-Heat Lung-Heat cough; pairs with Dang Gui, Fang Feng, Cang Zhu (Xiao Feng San framework) for Wind-Damp-Heat skin conditions. Modern pharmacology: strong anti-allergic action — inhibits allergic mediator release; anti-histaminergic properties.

3. Brighten the eyes and retreat membrane (tui yi):
Clears Liver-Fire and Liver-channel Wind-Heat; addresses eye redness, swelling, and pain; photophobia and tearing; eye dryness and grittiness from overuse; visual blurring from corneal opacity or conjunctival congestion. Tui yi specifically refers to retreating the opaque membrane (yi) that forms on the cornea from Liver-Heat accumulation — the classical indication for Chan Tui’s eye-brightening action. Pairs with Ju Hua, Gou Qi Zi, and Jue Ming Zi for Liver-channel Heat-related eye disorders.

4. Settle Wind and stop spasm:
Settles Liver-Wind stirring from Heat; calms limb spasm, muscle contracture, and convulsion. Addresses: paediatric fright-Wind (high fever with convulsion, convulsive stupor, locked jaw, limb rigidity — external Warm-pathogen type); nocturnal crying in children (internal Heat agitation producing nighttime crying and restlessness, ye ti); epilepsy (adjunctive, reduces seizure frequency); facial nerve spasm. Chan Tui’s settling action here is gentle and specifically directed at Heat-type Wind — it does not address Cold or deficiency-Wind patterns as effectively. Pairs with Tian Zhu Huang, Quan Xie for paediatric fright-Wind; pairs with Zhu Sha, Fu Shen in Bao Long Wan. Modern pharmacology: sedative and CNS-calming actions; muscle-relaxing properties that directly correspond to the spasm-settling action.

III. Four Classical Formulas

1. Yin Qiao San “Lonicera-Forsythia Powder” (Wen Bing Tiao Bian)
Composition: Jin Yin Hua · Lian Qiao · Chan Tui · Bo He · Niu Bang Zi · Jie Geng · Dan Zhu Ye · Gan Cao · Lu Gen · Jing Jie. Action: dispel Wind-Heat, clear Heat and detoxify. Indication: Wind-Heat exterior pattern — fever, mild or absent aversion to cold, head pain, sore and swollen throat, thirst; applicable to Wind-Heat cold, early-stage warm-pathogen diseases. Chan Tui’s role: enhance the light-dispersing Wind-Heat-releasing action and address voice hoarseness.

2. Ma Xing Shi Gan Tang with Chan Tui modification (Shang Han Lun)
Base: Ma Huang · Xing Ren · Shi Gao · Gan Cao; add Chan Tui to enhance rash-promoting and Wind-Heat-dispersing action. Action: clear and disperse Lung-Heat, stop cough and calm dyspnoea, promote rash eruption. Indication: Wind-Heat Lung-Heat — fever, cough with copious phlegm, shortness of breath; or incomplete measles rash eruption with accompanying respiratory symptoms. Chan Tui’s role: promote incomplete rash eruption outward while addressing the respiratory component.

3. Xiao Feng San “Dissolve-Wind Powder” (Wai Ke Zheng Zong)
Composition: Chan Tui · Jing Jie · Fang Feng · Ku Shen · Cang Zhu · Mu Tong · Shi Gao · Zhi Mu · Dang Gui · Sheng Di · Hei Zhi Ma · Gan Cao. Action: dispel Wind and clear Heat, dry Damp and stop itching. Indication: Wind-Damp-Heat skin conditions — urticaria, eczema, chronic recurrent skin itching, wind-rash, damp-rash; widespread body itching, scratching-induced redness, weeping or dry lesions. Chan Tui’s role: the primary Wind-dispersing and itch-stopping agent in this formula — its anti-allergic action is the key mechanism here.

4. Bao Long Wan “Protect-Dragon Pill” (classical paediatric formula)
Composition: Chan Tui · Tian Zhu Huang · (Zhu Sha · Fu Shen in classical version). Action: clear Heat and settle fright, calm Spirit and stabilise Mind. Indication: paediatric internal Heat fright-agitation — internal Heat causing restlessness and crying, nighttime fright-crying, sleep restlessness; also adjunctive for mild fright-Wind. Chan Tui’s role: the primary Wind-settling and Spirit-calming agent; Tian Zhu Huang adds Phlegm-dissolving and fright-settling support.

IV. Four-Herb Differential

V. Modern Pharmacology

Core chemical constituents: Chitin (jia ke su — the primary structural and pharmacologically active compound), multiple amino acids, and bioactive nutritional compounds.

Documented pharmacological actions:

• Anti-inflammatory: reduces various pharyngeal, skin-surface, and body-surface inflammatory responses; directly supports the Wind-Heat-clearing and throat-benefiting actions
• Sedative and Spirit-calming: calms emotional agitation; improves sleep; relieves anxiety and restlessness; directly supports the fright-settling and nocturnal-crying-calming actions
• Anti-allergic: strong inhibition of allergic mediator release; anti-histaminergic properties; directly supports the itching-relief and rash-settling actions; the best-documented modern pharmacological basis for Chan Tui’s clinical use in skin conditions
• Immunomodulatory: regulates immune function; enhances skin defence capacity
• Muscle-relaxing: relieves limb spasm and muscle contracture; directly supports the Wind-settling and spasm-stopping actions

Modern clinical applications:

• Dermatology: urticaria (qian ma zhen), seasonal dermatitis, eczema, persistent whole-body itching, drug-induced skin rash
• Paediatrics: internal-Heat paediatric nocturnal crying, fright-agitation, mild fright-Wind discomfort
• Daily wellness: Wind-Heat flare-up with sore throat, eye-screen fatigue with eye dryness, Wind-Heat voice hoarseness and simple adjustment

VI. Dosage and Safety

Dosage: decoction 3–6g; powder 1–1.5g twice daily; also used as single-herb tea for wind-heat sore throat and voice hoarseness.

Contraindications:

• G6PD deficiency (Favism, can dou bing): ABSOLUTE CONTRAINDICATION. Chan Tui is one of the few TCM herbs specifically documented to precipitate haemolytic crisis in G6PD-deficient patients. G6PD deficiency is common in Southeast Asian, South Chinese, and Mediterranean populations. All G6PD-deficient individuals must avoid Chan Tui without exception. This is the most clinically important safety consideration for Chan Tui and is unique among TCM herbs
• Cold-Damp constitution (yang deficiency, cold-aversion, loose stool): cold nature worsens interior Cold accumulation; use with caution; prefer lightly stir-fried form
• Pregnancy: no specialist TCM physician guidance; do not self-administer
• No long-term excessive use: continuous high-dose use depletes constitutionally Qi; produces fatigue and weakness
• Pattern specificity: indicated for Wind-Heat, Heat, or Liver-Wind patterns; contraindicated in pure Wind-Cold exterior patterns (without Heat signs) and Cold-Wind patterns