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Dan Du (Erysipelas) presents in various forms, yet its pathogenesis follows a single principle. It generally originates from Heart Fire (Heart Fire), where Wind-Toxicity (Wind-Toxin) clashes with the body's righteous Qi. The Heart governs the blood vessels; when blood is forced by fire, Yin stagnates within Yang, leading to heat and blood郁结 (stagnation) and rebellion. Internally, it steams and steeps, first accumulating in the chest and diaphragm; externally, it reaches the skin, becoming red due to heat, resembling cinnabar application, and hot as if roasted by fire. Whenever heat carries toxicity, severe toxicity causes extreme pain, gradually progressing to tissue necrosis, with fluid oozing from muscle fissures. If the toxin enters the Kidneys or abdomen, it becomes fatal.

Some cases exist from fetal life, where fetal toxin (Fetal Toxin) accumulates over time and erupts after birth upon exposure to heat. Others arise from the wet nurse's emotional distress (Seven Emotions), consumption of spicy, fried foods, or alcohol, allowing toxins to flow through breast milk and harm the infant. Some result from excessive feeding in children with weak Spleen Qi, causing heat accumulation internally and redness on the skin. Others stem from maternal fright during pregnancy, where fright-pathogen damages the fetus, transmitting sequentially and manifesting externally as night crying, slightly swollen eyelids, and a bluish-black complexion. Various types of Dan cannot be exhaustively listed. The general treatment principle is to clear fire and purge heat, causing the Dan to vanish instantly and the skin to recover.

Shi Yanshan stated: Fetal toxin-induced Dan occurs because fetal toxin lies dormant internally. It may be triggered by frequent bathing in hot water, wearing heated clothes, or the wet nurse's dietary indiscretion and internal heat from emotions, which aids the pathogen. It appears on the head, face, limbs, spreading to the chest and abdomen, presenting as red, wandering patches. Ancient texts state that cases starting from the limbs and entering the abdomen or scrotum are incurable. One should immediately suck the affected areas to gather toxic blood in one spot, then lance it with a bi stone (Bianshi). Administer Huoming Yin (Life-Saving Decoction) urgently. Lancing is contraindicated for infants under 100 days due to their delicate muscles. If excessive dispersal leads to deficiency-heat with persistent redness, use Buzhong Yiqi Tang (Tonify the Middle and Augment the Qi Decoction) with Fangfeng (Saposhnikovia Root) and Baizhi (Angelica Dahurica). If excessive cold-cooling herbs damage Stomach Qi causing persistent redness, use Yigong San (Yi Gong Powder) with Shengma (Cimicifuga Rhizome) and Chaihu (Bupleurum Root). If accompanied by convulsions, use Sijunzi Tang (Four Gentlemen Decoction) with Shengma, Danggui (Chinese Angelica Root), and Gouteng (Uncaria Ramulus cum Uncis). Further use of detoxifying agents will surely lead to death. For Dan on the forehead, lancing is appropriate.

Chao Yuanfang stated: In Huo Dan (Fire Dan) syndrome, symptoms fluctuate like Taiyang disease (Exterior Cold Syndrome), with red spots appearing on the body and expanding daily. He also described the appearance of Dan Hou (Dan Heat): skin turns red as if burned, forming blisters shortly thereafter.

*Shenghui Fang* (Holy惠民 Formulas) stated: All pediatric Dan results from wind-toxicity residing in the couli (interstices) and heat-toxicity clashing with blood, evaporating outward. The skin becomes hot and red, resembling cinnabar, hence the name Dan. If unceasing, muscles rot. If toxin enters the abdomen, it is fatal. Thus, a single formula treats all, called "Yiqie Dan" (All Dan). Use Shengma San (Cimicifuga Powder). Chi Dan (Red Dan) is caused by heavy wind-toxicity, resulting in redness. Initially swelling like linked coins or small beans, with millet-grain-like elevations on the flesh resembling rooster combs, it is also called Zhuyu Dan (Cornel Dan). Apply Shengma Gao (Cimicifuga Ointment). Tianhuo Dan (Heavenly Fire Dan) features red patches in the flesh, palm-sized or widespread with intense itching. Treat back-originating Tianhuo Dan with Sangbaipi (Mulberry Root Bark) powder mixed with sheep fat. *Qianjin Fang* treats Tianhuo Dan starting from the thigh; for infants under 100 days touching "road stove gods," if heat flows to the glans causing swelling and bleeding, apply Fulonggan (Dragon's House Soil) powder mixed with egg white. Guihuo Dan (Ghost Fire Dan) appears on arms, red like plums; treat with Rongyan San. Yehuo Dan (Wild Fire Dan) presents as plum-sized red spots covering the back and abdomen; widespread redness is also Yehuo Dan. Mix Xionghuang (Realgar) and Rongyan (Rock Salt) each 5 qian, apply with egg white frequently until healed. Jiahuo Dan (House Fire Dan) starts on cheeks, arms, and axillae; ancient formulas for throat/abdominal invasion use Xiaoshi (Niter) and Ningshuishi (Halloysite), dried in copper, powdered, and taken as a cubic inch dose. Yanghuo Dan starts on flanks/axillae/legs; take Puxiao (Mirabilite) powder 5 fen with bamboo juice, adjusted by age. Shenhuo Dan (Divine Fire Dan) appears on arms, turning dark red/black within a day; apply Zhi Zi (Gardenia Fruit) powder mixed with vinegar. Yinghuo Dan burns intensely on flanks, starting at forehead/ears with pain; mix Xiaodou (Adzuki Bean) 1 he, Xiaoshi 5 qian, Hanshuishi (Calcitum) 1 fen, take 5 fen with cold water three times daily, adjusted by age. Can also be applied topically. Zhutianhuo Dan starts on back, becoming sores in 24 hours; apply Landian (Indigo). If no sore, apply Adzuki bean powder with egg white; if sore, sprinkle bean powder. Tianzao Huo Dan starts on inner arms/buttocks, flowing to glans with swelling/bleeding; mix Adzuki bean and Fulonggan equally, apply with egg white. Cheqianzi (Plantago Seed) powder with water is also effective. Feizao Huo Dan starts on dorsum pedis, bright red; mix Xiaodou 1 liang, Niujiao (Ox Horn) 2 liang, calcined to ash, apply with egg white. Niazao Huo Dan starts above knees/thighs/navel, flowing to glans; apply Li shu gen (Li Tree Root) ash mixed with field stream water. Chil Liu (Red Flow) presents as rouge-colored patches spreading on the body, known as Liuhuo (Flowing Fire). Heat-induced is red; wind-induced is white; both swell with high fever. Lance evil blood first, then administer Shengma Tang (Cimicifuga Decoction). Curable if toxin hasn't entered abdomen. Shechan Dan (Snake-Wrapping Dan) wrapping the waist is fatal; apply crushed lettuce or seeds. Zhizhu Dan (Spider Dan) covers the body; apply BaiFan (Alum), Zaojiao (Tamarisk Pod) ash, and pig trough mud. Chi Bai Youzhong (Red-White Wandering Swelling) occurs in children with deficient flesh, where wind-heat attacks, clashing with blood/qi, causing red swelling. Wind moves with qi, wandering不定 (indefinitely). It shows blue/yellow/red/white colors without fixed hue, wandering under skin with slight sheen. Use Xijiao San (Rhinoceros Horn Powder). For Dan entering abdomen, apply raw sesame oil and administer Yingru Fang. For Dan pain, drink 1 sheng of Zhuru (Bamboo Shavings) juice, effective in 1-2 doses. For Dan itch, mix Leijiu (Leek Juice) with salt and sesame oil, warm by rubbing, and wipe on Dan for instant relief.

Zeng Shi stated: Chi Huo Dan Liu (Red Fire Dan Tumor) stems from internal Heart Fire heat, red as cinnabar. Heart governs blood; fire is hot. Blood-heat clash causes Yin stagnation in Yang, triggering Dan. Heart deficiency-cold causes itching; Heart excess-heat causes pain. Dan originating from abdomen to limbs is easy to treat; limbs to abdomen is difficult. First use Baijie San (Hundred Resolutions Powder) to release exterior, then Danggui San (Angelica Powder) with Qiaojiao (Forsythia) and Jingjie (Schizonepeta) decocted in water to vent heat and extract toxin. Alternatively, Chige San or Hudan Tang. If accompanied by floating rash, lethargy, and irritability, it is Yin-Damp Toxic Syndrome. Infants (under 100 days or over 6 months) with sudden red eyelid rims, dark-blue face, night crying, or rouge-like face have latent heat. If caused by maternal fright damaging fetus, it manifests externally. Initial presentation resembles water beans on face, slightly red feet, intermittent. Spreading to neck like cinnabar is called Jing Dan (Fright Dan). Use Sisheng San. Wash eyes first, then decoct Baijie San with Wuhe Tang to resolve fright-heat/Dan. Danggui San or Niubang Tang are alternatives. If Jing Dan spreads to chest/breasts with phlegm-wheeze/convulsions, urgently vent heat/toxin to prevent internal spread. Use Wuhe Tang with Shengma, Shengdi (Rehmannia), Dengxincao (Juncus Effusus), and Shengjiang (Fresh Ginger) to eliminate. Continue previous medicines to prevent complications.

Wu Shou stated: Pediatric Dan Du is extreme heat-toxicity clashing with blood, invaded by wind, causing red swelling and wandering rash, also called Chi You Feng (Red Wandering Wind). Entering abdomen/Kidneys is fatal. Although diverse, the source is one. Widespread red Dan with itching, or girls aged 15-16 with unopened menses developing Dan rashes, are due to wind-toxicity invading blood. Use Fangji San (Stephania Powder).