Zhang Zhongjing merely named Yin Du (Yin Toxin) as a condition primarily treated with exterior-releasing methods.

Yin Du (Yin Toxin) is characterized by a bluish complexion, body pain resembling that of being beaten with a staff, and sore throat. If treated within five days of onset, it is curable; if treatment begins after seven days, it becomes difficult to cure. The primary formula is Shengma Biejia Tang (Cinnamon Twig and Turtle Shell Decoction), modified by removing Xionghuang (Realgar) and Shujiao (Sichuan Pepper) (see the section on Yang Du).

Wang Kentang’s examination: Although Zhang Zhongjing’s texts mention the name "Yin Du," the symptoms described are limited to a bluish face, body pain like being struck by a staff, and sore throat. There is no mention of extreme Yin-cold conditions. Furthermore, the formulas used do not include strongly warming or hot herbs, consisting only of Shengma (Cimicifugae Rhizoma), Gancao (Glycyrrhizae Radix et Rhizoma), Danggui (Angelicae Sinensis Radix), and Biejia (Testudinis Carapax et Plastrum). Thus, Zhang Zhongjing’s "Yin Du" does not refer to a Yin-cold disease but rather to an invasion of malignant, abnormal Qi from heaven and earth into the Yin meridians, hence the name "Yin Du." Later physicians, however, assumed this referred to extreme Yin-cold conditions. They combined Zhang’s descriptions of bluish face, body pain, and sore throat with treatments using strongly warming formulas such as Fuzi San (Aconite Powder) and Zhengyang San (Upright Yang Powder). I believe that while extreme Yin-cold conditions can be named Yin Du, this is not Zhang Zhongjing’s original intent. The Yin Du described by later authors differs significantly from Zhang’s description and should not be conflated. Later descriptions of Yin Du typically arise from internal injury by cold foods, exposure to sudden violent cold, excessive consumption of cold-cooling medicines, or simultaneous external and internal cold injury, rather than infection by malignant abnormal Qi.

The *Liuren Shu* renames Yin Du as "Yin Du Shanghan" (Yin Toxin Cold Damage) and advocates treating it by retreating Yin.

**Yindu Gancao Tang (Yin Toxin Licorice Decoction)** treats Shanghan (Cold Damage) or seasonal qi diseases where Yin Du forms within one or two days of onset, or develops between six to ten days after medication. Symptoms include heavy body, stiff back, colicky abdominal pain, difficulty in the throat, toxic heat attacking the heart, hardness below the heart, shortness of breath, vomiting, cyanotic lips, blackish complexion, cold extremities, and a deep, fine, and rapid pulse. The body feels as if beaten, with a sore throat. Curable within five to six days; incurable after seven days.

Ingredients: Zhi Gancao (Honey-fried Glycyrrhizae Radix et Rhizoma), Guizhi (Cinnamomi Ramulus, bark removed), Shengma (Cimicifugae Rhizoma), Danggui (Angelicae Sinensis Radix) [each 5 qian]; Xionghuang (Realgar) [2.5 qian]; Shujiao (Zanthoxyli Pericarpium, remove closed ones, stir-fry until sweat evaporates and remove seeds) [5 qian]; Biejia (Testudinis Carapax et Plastrum, fried in butter) [1.5 liang]. Chop ingredients, decoct in water. Take one dose; after walking for the distance covered in five li, take another dose. Cover with blankets to induce sweating; toxins exit via sweat, and recovery follows. If sweating does not occur, administer again.

Initial Yin Du presents with a deep, fine, and rapid pulse. Xu Shuai states: Yin Du originates from deficiency-cold of Kidney Qi, often triggered by sexual activity or consuming cold foods followed by wind-cold invasion. Internal latent Yin combines with external cold, or external cold precedes internal latent Yin, resulting in dual Yin conditions where Yang Qi fails to maintain control. Symptoms include headache, heavy waist, abdominal pain, eye pain, lethargy without significant fever, cold extremities, cold sweat on forehead and dorsum of hands, irritability/thirst, mental confusion, or ability to walk but feeling heavy. Pulse is deep, fine, and rapid in all six positions, with a short Chi position; Cun position may be imperceptible. If pulses are floating and large, or deep and large but not rapid, it is not a Yin syndrome. Excessive use of cooling medicines exacerbates thirst and irritability. Urgently administer Huanyang Tuiyin (Restore Yang and Retreat Yin) medicines to stabilize the condition, focusing on tonifying deficiency and harmonizing Qi. Suitable formulas include Zhengyuan San (Primary Origin Powder), Tuiyin San (Retreat Yin Powder), and Wusheng San (Five Virtues Powder). Sweating is contraindicated in Yin syndromes unless Qi is sufficient, pulse is large, and fever persists, in which case sweating medication is permissible.

**Zhengyuan San (Primary Origin Powder)** treats Shanghan where wind-cold affects limbs, head, eyes, and bone joints. Take urgently; repeat after walking five li; continue for three doses to induce immediate sweating. For Yin Du Shanghan, add 5 fen of Tuiyin San. Also effective for dizziness, qi stagnation, and various heart/abdominal disorders caused by cold or food injury.

Ingredients: Mahuang (Ephedrae Herba, nodes removed), Chenpi (Citri Reticulatae Pericarpium), Dasheng (Rhei Radix et Rhizoma, raw), Gancao (Glycyrrhizae Radix et Rhizoma), Ganjiang (Zingiberis Rhizoma), Rougui (Cinnamomi Cortex), Shaoyao (Paeoniae Radix), Fuzi (Aconiti Lateralis Radix Praeparata), Wuzhuyu (Evodiae Fructus), Banxia (Pinelliae Rhizoma Praeparatum) [equal parts]. Chop ingredients. Increase Mahuang by half; decrease Wuzhuyu by half. Grind to powder. Take 1 qian per dose with 1 sheng water, 3 slices of fresh ginger, and 1 jujube. Decoct to 0.7 sheng. Drink hot. Cover to induce sweating. Remove covers only after sweat dries. Do not use Mahuang for Yin Du to avoid excessive sweating.

**Tuiyin San (Retreat Yin Powder)** treats Yin Du Shanghan with cold extremities, deep/fine pulse, headache, and heavy waist. Effective for minor cold injuries after three doses. Take 1 zi per dose mixed with Zhengyuan San, plus a pinch of salt. For coughing/counterflow qi in Yin Du Shanghan, decoct one dose and sip slowly while warm until symptoms cease.

Ingredients: Chuanwu (Aconiti Radix), Ganjiang (Zingiberis Rhizoma) [equal parts]. Coarsely grind, stir-fry until color changes, cool, then finely grind. Take 1 qian with 1 sheng water and a pinch of salt. Decoct to 0.5 sheng, strain, and drink warm.

**Wusheng San (Five Virtues Powder)** treats Shanghan with headache, high fever, bone/joint pain, drowsiness, cough, nasal congestion, and loss of appetite. Also effective for Shanghan complicated by cold qi and chronic Yin Du.

Ingredients: Baizhu (Atractylodis Macrocephalae Rhizoma) [1.5 liang], Gancao (Glycyrrhizae Radix et Rhizoma), Wuweizi (Schisandrae Chinensis Fructus), Shigao (Gypsum Fibrosum) [each 1 liang], Ganjiang (Zingiberis Rhizoma) [3.5 liang]. Chop. Take 5 qian with 1 sheng water and a little salt. Decoct together. For cold qi complications, add ginger and jujube. For Yin Du, add mugwort leaves.

**Haizang’s Baizhu San (Atractylodes Powder)** treats Yin Du Shanghan with chest oppression, irritability, and cold extremities.

Ingredients: Chuanwu (Aconiti Radix, processed, peel and core removed), Jiegeng (Platycodonis Radix), Fuzi (Aconiti Lateralis Radix Praeparata), Baizhu (Atractylodis Macrocephalae Rhizoma), Xixin (Asari Radix et Rhizoma) [each 1 liang], Ganjiang (Zingiberis Rhizoma, processed) [0.5 liang]. Chop or grind. Mix with warm water and take 1 qian bi.

**Luo Zhidi’s Zhengyang San (Upright Yang Powder)** treats Yin Du Shanghan with cold extremities, cyanotic nails, cold body, and deep/fine/micro pulse. Highly effective. Use 4-5 stalks of scallion and 4-5 old hornet nests, burn until charred but retain nature, grind to fine powder. Mix with scallion juice, form pills like quail eggs. Hold in palm, tie tightly with handkerchief. Sweat will appear shortly; cover with cotton blanket. If palm becomes too hot, do not untie. Prior to taking this, first take Shengma Tang (Cimicifuga Decoction): 5 qian Shengma, 3 stalks of scallion with roots, 5 slices of ginger, 2 large sheng water. Decoct to 1 sheng, strain, drink warm, cover to induce sweat.

As Yin Du deepens, nails turn blue, face turns black, pulse reaches seven beats per respiration, and is deep/fine.

Accumulated Yin at the lower burner causes slight Yang to dissipate at the upper burner. Symptoms include heavy/cold extremities, worsening abdominal pain, throat obstruction, chest fullness/hardness, irritability/thirst, continuous cold sweat, occasional delirium, cyanotic nails/face, and a fine pulse beating seven times per respiration or more. Immediately moxa Qihai (CV6) and Guanyuan (CV4) points 200-300 moxibustions until extremities warm. Continue administering Jin Ye Dan (Golden Liquid Pill), Lai Su Dan, Wusheng San, Huanyang San, and Tuiyin San.

**Yunü San (Jade Maiden Powder)**:
Chuanwu (Aconiti Radix, peel/core removed, soak in cold water for 7 days, slice thinly, dry, store in paper bag). For patients, take 1 major qian powder, mix with 1 small qian salt, 1 sheng water. Decoct to 0.7 sheng. This suppresses Yin Du toxin, expelling material resembling pig blood. Repeat if necessary.

**Huanyang San (Restore Yang Powder)** treats Yin Du with blue face, cold extremities, irritability, and abdominal pain.
Usage: Mix sulfur powder with fresh well water, take 2 qian. After a while, chills or fever may arise; adjust dosage accordingly. Recovery occurs with sweating.

**Fuzi Huanyang San (Aconite Restore Yang Powder)** from *Liang Fang* treats Yin Du Shanghan with blue face, four reversals (cold extremities), and umbilical/abdominal pain, icy body, and sudden severe cold qi.
Usage: Process 2 Fuzi (remove peel/core), grind to powder. Take 3 qian bi, mix with 0.5 sheng fresh ginger juice and cold wine (total 1 sheng). Swallow with another sheng of cold clear wine. Repeat after a short while. Recovery is indicated when warmth spreads from below the navel throughout the body.

**Liuren’s Fanyin Dan (Return Yin Pill)** treats Yin Du Shanghan with mental irritability, headache, and cold extremities.
Ingredients: Liuhuang (Sulfur, 5 liang, separately ground), Fuzi (Processed Aconiti Lateralis Radix Praeparata), Ganjiang (Processed Zingiberis Rhizoma), Guixin (Cinnamomi Cortex) [each 0.5 liang], Xiaoshi (Natrii Nitras, separately ground), Taiyuan Yuanjingshi (Taiyuan Yuanjingshi, separately ground) [each 2 liang].
Usage: In a cast iron pot, layer half the Yuanjingshi powder, then half the Xiaoshi powder. Place Sulfur powder in the middle, cover with remaining Xiaoshi, then top with remaining Yuanjingshi. Seal with a small cup. Burn with 3 jin charcoal until properly heated, avoiding smoke. Grind finely to flour-like consistency. Mix the three powders with the previous medicine. Form pills with soft rice dough, size of wuweizi (Chinese honeylocust seed). Take 15-20 pills with decocted mugwort water frequently until sweating occurs. For severe cases, take 30 pills. This formula is very effective; it stops wheezing and vomiting upon ingestion. If symptoms persist after 3-5 doses, moxa 1 cun below the navel. Moxa continuously day and night without limit on number of cones. Use adequate cone size for efficacy. If hands/feet are cold and lower abdomen hard, moxa two lines 1 cun lateral to the midline below the navel, plus the midline point (three points total). Combine with Danggui Sini Tang (Angelica Decoction for Four Reversals) and Fanyin Dan, taken frequently to ensure internal/external penetration. Delay leads to death. If Yin syndrome includes lower abdomen obstruction, retracted testicles, and severe abdominal pain nearing death, urgently moxa Shimen (CV5), 2 cun below the navel. Combine with Fanyin Dan and Danggui Sini Tang plus Wuzhuyu and ginger. Avoid standard diuretic or cold-slippery medicines.

**Huoyan San (Flame Powder)** treats severe Shanghan complications.
Ingredients: Bo Shang Liuhuang (Imported Sulfur), Hei Fuzi (Black Aconiti Radix, raw, peeled), Xin La Cha (New Wax Tea) [each 1 liang]. Grind to fine powder. Mix 1 sheng good wine with powder, spread in a new bowl. Dry over fire, place on tile. Under each bowl, burn 1 fist-sized amount of cooked mugwort. Cover with tile to prevent ignition until smoke ceases. Scrape cooled residue into porcelain box. Take 2 qian with 1 sheng wine, decoct to 0.7 sheng. Flames may rise; do not be alarmed. For Yin Du Shanghan with cold extremities, deep/fine pulse, vomiting/diarrhea, five-heart irritability, chest hardness, early latent Yin preventing fluid intake, or absent pulse: Take one dose. If vomiting occurs, take another. Heart warmth indicates recovery. If pathogens descend to organs but exterior remains unresolved, high fever and surging pulse indicate need for exterior-releasing medicine. If exterior resolves, sleep ensues with sweating. If slight stagnation and solid pulse remain, use purgatives for organs. Gradually use harmonizing tonics for spleen/stomach. If unresponsive after three doses, it is incurable.

Severe Yin Du with eight-beat pulse indicates deep pathology.

Severe Yin Du symptoms resemble earlier stages but are heavier. Pulses are only palpable when pressed deeply against the bone; superficial pressure yields nothing. Pulse rate exceeds normal limits, making medication ineffective. Moxa 300+ cones (date-sized) below the navel. If extremities do not warm, it is incurable. If condition stabilizes, assist with sulfur and hot medicines. As Yin dissipates and Yang returns, gradually reduce hot medicines and treat harmoniously for recovery.

**Liuren’s Congbai Wei Fa (Scallion White Ironing Method)** treats Yin deficiency with Yang collapse, cold body, absent pulse, impending respiratory failure, unconsciousness, and refractory Yin Jue (Cold Reversal). Bind scallions like an arm, chop thickly, remove roots/leaves, keep white parts ~2 cun long, shape like a large pancake. Heat one side with fire (do not ignite), then iron onto patient’s umbilicus and below. Use a hot ironing tool filled with fire to press scallion pancakes, driving heat into muscles. Replace 3-4 pancakes as needed. Patient should regain consciousness, warm extremities, and sweat. Follow with Sini Tang (Four Reversals Decoction) to warm interior.

**Haizang** notes that for Yin syndromes unresponsive to drugs, inability to swallow fluids, cold body, absent pulse, short breath, and unconsciousness, the scallion ironing method is less effective than steaming bran mixed with strong vinegar in a cloth bag and ironing. This latter method is faster.

**Daijiu Tuqi Gao (Moxa-Replacing Navel Paste)**:
Ingredients: Fuzi (Aconiti Lateralis Radix Praeparata), Malanzi (Portulacae Semen), Shechuangzi (Cnidii Fructus), Wuzhuyu (Evodiae Fructus), Rougui (Cinnamomi Cortex) [equal parts]. Grind to powder. Mix 1 spoon flour, 1 spoon powder, and fresh ginger juice to form paste. Apply on paper, circle ~3 cun, stick to Guanyuan (CV4) and Qihai (CV6) below navel from evening to morning. Heat power equals 100 moxibustions. Also for lower back pain. Alternative: Grind Dingxiang (Caryophylli Flos), Bibo (Piperis Kadsurae Fructus), Ganjiang (Zingiberis Rhizoma), Moli (Ostreae Concha calcined to ash). Place in palm, mix with saliva to mud, cover genitalia with hand until warm sweat appears.

For Yin Du Shanghan with cold extremities, use Wuzhuyu (Evodiae Fructus) ground to powder, mixed with warm wine, placed in silk bag, and ironed on soles of feet until circulation restores. Alternatively, wash limbs with warm decocted medicines.

**Huisheng Sheng Gao (Life-Restoring Divine Ointment)** from *Liang Fang* treats external application for male/female Yin Du Shanghan.
Ingredients: Moli (Ostreae Concha, powdered), Ganjiang (Processed Zingiberis Rhizoma) [1 qian each]. Grind to powder. For males, mix with female saliva, rub hands warm, press firmly over testes until sweat appears. For females, mix with male saliva, rub hands warm, press firmly over breasts until sweat appears. Testicles and breasts are root centers of Yin/Yang and Kan/Li divisions. For Yin syndrome with urinary/fecal retention or miscellaneous Yin syndromes, this external method is suitable. Urgent if retention lasts several days; otherwise avoid.

**Yin Zhong Fu Yang (Latent Yang within Yin): Poyin Dan (Break Yin Pill)**.
Ingredients: Liuhuang (Sulfur), Shuiyin (Mercurius) [each 1 liang], Chenpi (Citri Reticulatae Pericarpium), Qingpi (Citri Reticulatae Pericarpium Viride) [each 0.5 liang]. Melt sulfur in pot, add mercury, beat with iron rod until uniform. Pour into black tea cup, grind finely. Add Chenpi and Qingpi, form pills with wheat paste, size of wuweizi. Take 30 pills. For irritability, take with cold salt water; for Yin syndrome, take with mugwort water for good effect.

Case: Patient initially presented with cold extremities, stabbing pain below navel, body pain like being beaten—indicative of Yin syndrome. Urgently administered Jin Ye Dan, Poyin Dan, and Laifu Dan. Pulse became deep and slippery. Deep indicates Yin; slippery indicates Yang. Seeing Yang pulse in Yin syndrome suggests potential for survival, as Zhang Zhongjing stated: "Yang pulse in Yin disease indicates life." Moxa Qihai and Dantian 100 times. When extremities warm and Yang returns, sweating resolves the condition. Question: Why does a slippery/deep pulse indicate life? Answer: Zhang Zhongjing said, "Xi yan chen ming yue hua" (Fluttering suddenly sinking is called slippery). Deep is pure Yin; Xi (fluttering/opening) is correct Yang. Harmony of Yin and Yang creates slipperiness. Ancient texts describe slippery pulse as smooth and rotating, similar to rapid pulse. Zhang’s three words suffice. "Xi" means opening/converging, representing Yang. "Chen" means sinking, representing Yin. "Yan" means suddenly. Between opening and sinking lies the slippery quality. These terms are precise but difficult to understand; readers must ponder carefully.

**Pili San (Thunderbolt Powder)** treats Shanghan where Yin excess blocks Yang. Patients exhibit irritability/heat but no desire to drink.
Usage: Burn 1 Fuzi to ash (retain nature), grind to powder. Take one dose mixed with honey water. Recovery occurs as cold qi is forced out, heat rises, and sweat appears.

**Tao Hua** states: For Yin Du with cyanotic nails and deep/fine/rapid pulse, use Sini Tang. For absent pulse, use Tongmai Sini Tang (Pulse-Returning Four Reversals Decoction). Other selectable formulas include Yindu Gancao Tang, Zhenwu Tang (True Warrior Decoction), Houpo Wan (Magnolia Bark Pill), Baizhu Tang, and Rougui San.
Formulas for restoring Yang/retreating Yin: Pili San, Zhengyuan San, Tianxiong San, Fuzi San.

**Jie Shi**: Jin Ye Dan (Golden Liquid Pill).

**Xun Shi**: For cold reversal and retracted testicles, roast beans, throw into hot vinegar, and fumigate according to method.

**Ironing and Moxibustion Methods**:
1. Shanghan directly invading Yin meridians (true cold) or Yin Du: Body pain like being beaten, colicky abdominal pain, vomiting, heaviness, unconsciousness, rigid/cold limbs, cyanotic nails/lips, inability to take oral meds, deep/fine or absent pulse. Take 1 bundle of scallion whites (~3 cun), mash into cake. Fill umbilicus with 0.5 fen Moshe (Moschus). Place scallion cake on umbilicus. Iron with fire, replacing 3-4 cakes. Once slightly conscious, pour fresh ginger juice, administer Huiyang Jiuti Tang (Restore Yang and Rescue Extremity Collapse Decoction). If still unconscious, moxa Qihai and Guanyuan 20-30 times to drive heat inward, expel evil, and restore Yang. If extremities warm and sweat appears, there is hope. If not, prognosis is poor.

**Wu Kun** asks: Why take Fuzi Tang cold for Yin Du Shanghan? This treats Yin extreme at bottom with floating Yang at top. Case: Patient with Shanghan for 10+ days, deep/fine pulse, warm hands/cold feet, constipation, red face, vomiting/irritability/thirst, unable to keep meds down, preferring cold water/watermelon. Internal Yin cold forces floating Yang/fire to gather in chest, rising to throat, causing red face/vomiting. Used 1 large Fuzi wrapped in ginger juice and flour, baked, peeled, sliced. Decocted with 3 qian Ren Shen (Ginseng Radix) and 3 qian Pao Ganjiang (Processed Zingiberis Rhizoma) in 2 zhong water to 1 zhong. Soaked in cold water until cool, then administered. Recovered. *Neijing* states: "To regulate cold/heat reversal, cold/hot administration is necessary. Hot medicine taken cold: once cold body dissipates, hot nature activates, curing disease without violating stomach comfort." Modern practitioners hesitate to use Fuzi for Yin syndrome until Yang is exhausted, which is too late. Treat disease with appropriate medicine; do not hesitate. For Jia Yin Shanghan (complicated Yin Cold Damage), initial sexual activity causes latent Yin internally, compounded by external cold. Dual Yin leads to Yin dominance and Yang decline, causing deep pulse and cold feet. Urgently use Ren Shen to support Qi and Fuzi to warm Kidney and dispel cold, retreating Yin and restoring Yang. Without these, how to save the patient? Proverb: "Shanghan tends to kill those with deficient lower bodies." True words. Xu Xueshi emphasizes preserving True Qi (vital energy), the root of life. Ignoring Qi deficiency to attack heat with sweating/purgation or cold medicines worsens Yin cold, leading to critical danger.

**Another Formula**: Drop rooster blood into non-ash hot wine, drink, cover with blankets to induce sweat.