汗者。气分之水。其源出于膀胱。内经云。膀胱者。州都之官。津液藏焉。气化则能出矣。膀胱之气。从三焦。行
腠理。充肌肉。达于皮毛。以卫外为固。阳气卫外。百邪不入。故其经称为太阳也。其有盛暑天气。亢阳蒸动
膀胱水气。腾布于外。则发为汗。此犹天之有雨。阳布阴和。自然无病。有时外感风寒。皮毛疏泄。发热汗出
者。乃太阳之气。为邪所病。不能卫外。故汗得泄出。其有心胃肝脾热湿之病。亦令汗出者。此犹土润溽暑。
亦能蒸作云雨也。又有亡阳自汗者。则由膀胱肾中之元阳脱泄。故其水阴之气。随而奔溢。散涣不收。气
为水之所化。水即气也。汗即水也。气脱外泄。故汗出也。知此。则知汗出气分。不出血分矣。然汗虽出于气
分。而未尝不与血分相关。故血分有热。亦能蒸动气分之水。而为盗汗。盖血气阴阳。原互根互宅。阴分之
血盛。则阳分之水阴。自然充达。阳分之水阴。足以布护灌濡。则阴分之血。愈为和泽。而无阳乘阴之病矣。
若阳分之水阴不足。则益伤血之阴。故伤寒汗出过多。则虚烦不寐。以其兼伤血分之阴。心主血分。血分
之阴伤。则心气为之不宁矣。又有伤寒。即当从汗而解。今不得汗。乃从鼻衄而愈。其衄名为红汗。盖阳分
之邪。宜挟阳分之水。发而外出。今既不能外出。乃乘阴分之血。从鼻衄出。名为红汗。是为阳邪干阴之一
验。故古谓阳乘阴。则吐衄。知阳乘阴而内逆者。发为吐衄。则知阳乘阴而外泄者。发为皮肤血汗矣。血者。
心之液也。皮毛者肺之合也。治法。宜清心火。火清则阳不乘阴。兼治肺金。肺调则皮毛不泄。凉血地黄汤。
加桑皮地骨皮蝉蜕百合蒲黄治之。血虚火甚者。当归六黄汤治之。气虚血少者。当归补血汤。加桑皮地
骨丹皮蝉蜕棕榈炭黄芩秦皮治之。外用锻石散扑之。仿仲景汗出不止。用温粉扑法之意也。或用桃花
散扑之亦可。
皮毛者。肺之合也。汗出皮毛。故汗血宜治肺金。以敛皮毛。人参清肺汤。加蒲黄最宜。血者。肝之所司也。肝
火亢烈。逼血妄行。宜当归芦荟丸。从内以攻治之。喻嘉言治女子经血闭。而周身汗出者。谓是阴分之热。
泄出阳分。用此方破经血。即以苦坚止汗。汗血同源。若肝火亢甚。而汗血者。借用此方。尤为合法。
胃火亢甚。亦能汗血。以胃主肌肉。热蒸肌肉。故令汗血。宜竹叶石膏汤。加蒲黄蝉蜕丹皮治之。犀角地黄
汤。亦治之。
总论曰。汗者。阳分之水。血者。阴分之液。阴与阳原无间隔。血与水本不相离。故汗出过多则伤血。下后亡
津液则伤血。热结膀胱则下血。是水病而不离乎血者也。吐血咳血。必兼痰饮。血虚则口渴而津液不生。
失血家往往水肿。瘀血化水。亦发为肿。是血病而不离乎水者也。故衄血家不可再发汗。以血病则阴液
既虚。不可发汗。再伤气分之水。以致阳分之液亦虚也。又先水肿再吐血者。不治。以水病不可重伤其血
也。观小柴胡调津液。而即治热入血室。观桃仁承气破血结。而即治小便不利。皆是治水。即以治血。治血
即以治水。盖在下焦。则血海膀胱。同居一地。在上焦。则肺主水道。心主血脉。在躯壳外。则汗出皮毛。血循
经脉。一阴一阳。皆相联属。吾于水火血气论已详言之。人必深知此理。而后知治血理气。调阴和阳之法。
可以左右逢源。
汗，是气分中的水液。它的源头在于膀胱。《内经》说：膀胱，是州都之官，津液藏聚于此，经过气化作用才能排出。膀胱的气，通过三焦，运行于腠理（皮肤肌肉的间隙），充盈肌肉，通达皮毛，以此护卫体表以固密。阳气护卫体表，百邪不得侵入，所以其经脉称为太阳经。如果有盛暑天气，亢盛的阳气蒸动膀胱的水气，腾涌散布于体外，就发为汗。这就像天上有雨，阳气布散、阴气和合，自然没有疾病。有时外感风寒，导致皮毛疏泄，出现发热汗出的症状，这是太阳经之气被邪气所困，不能护卫体表，所以汗得以泄出。那些有心、胃、肝、脾热湿病的患者，也会令汗出，这就像土地湿润、湿热熏蒸，也能蒸发成云雨一样。又有亡阳导致的自汗，则是由于膀胱和肾中的元阳脱失泄漏，所以其水阴之气随之奔涌溢散，涣散不收。气被水所化，水即是气；汗即是水。气脱而外泄，所以汗出。明白了这一点，就知道汗出于气分，不出于血分。然而汗虽然出于气分，却未尝不与血分相关。所以血分有热，也能蒸动气分的水液，而为盗汗。盖因气血阴阳，原本互根互宅。阴分的血盛，则阳分的水阴自然充达；阳分的水阴足以布护灌濡，则阴分的血更加和泽，而没有阳乘阴的病变了。如果阳分的水阴不足，就会进一步损伤血的阴液。所以伤寒病中汗出过多，会导致虚烦不寐，因为兼伤了血分之阴。心主血分，血分之阴受伤，则心气为之不宁。又有伤寒病，本应当从汗而解，现在不得汗，而是从鼻衄而愈。这种衄血名为“红汗”。盖因阳分之邪，宜挟带阳分的水液，发散而外出。现在既不能从表外出，便乘袭阴分之血，从鼻衄而出，名为红汗。这是阳邪干犯阴分的一个验证。所以古人说阳乘阴，则发生吐衄。知道阳乘阴而内逆者，发为吐衄；就知道阳乘阴而外泄者，发为皮肤血汗了。血，是心的体液。皮毛，是肺的外合。治疗方法，宜清心火，火清则阳不乘阴；兼治肺金，肺调则皮毛不泄。用凉血地黄汤，加桑白皮、地骨皮、蝉蜕、百合、蒲黄治疗。血虚火甚者，用当归六黄汤治疗。气虚血少者，用当归补血汤，加桑白皮、地骨皮、丹皮、蝉蜕、棕榈炭、黄芩、秦皮治疗。外用锻石散扑洒。仿效张仲景汗出不止，用温粉扑法的意思。或者用桃花散扑洒也可以。
皮毛是肺的外合。汗出于皮毛，所以汗血宜治肺金，以收敛皮毛。用人参清肺汤，加蒲黄最为适宜。血，由肝所主管。肝火亢烈，逼迫血液妄行，宜用当归芦荟丸，从内部攻治。喻嘉言治疗女子经血闭阻，而周身汗出的情况，认为是阴分之热，泄出于阳分，用此方破除经血，即以苦坚之法止汗。汗血同源，若肝火亢盛而导致汗血者，借用此方，尤为合法。
胃火亢盛，也能导致汗血。因为胃主肌肉，热蒸肌肉，所以令汗血。宜用竹叶石膏汤，加蒲黄、蝉蜕、丹皮治疗。犀角地黄汤，也能治疗。
总论说：汗，是阳分的水；血，是阴分的液。阴与阳原本没有间隔，血与水本来不相分离。所以汗出过多则伤血，下法后亡失津液则伤血，热结膀胱则下血，这是水病而不离乎血的情况。吐血咳血，必兼痰饮，血虚则口渴而津液不生，失血的人往往水肿，瘀血化水，也发为肿，这是血病而不离乎水的情况。所以衄血的人不可再发汗，因为血病则阴液已经虚弱，不可再发汗，以免再次伤及气分的水，以致阳分的水液也虚弱。又如果先水肿再吐血者，属于不治之症，因为水病不可重伤其血。看小柴胡汤调和津液，就能治疗热入血室；看桃仁承气汤破除血结，就能治疗小便不利，这些都是治水即治血，治血即治水。因为在下面焦，血海和膀胱同居一地；在上面焦，肺主水道，心主血脉；在躯壳之外，汗出于皮毛，血循行于经脉。一阴一阳，皆相互联属。我在《水火血气论》中已经详细论述过。人必须深知这个道理，然后才知道治血理气、调阴和阳的方法，可以左右逢源。
Sweat is the fluid within the Qi aspect. Its source lies in the Bladder (Pang Guang, 膀胱). The *Neijing* states: "The Bladder is the official of the capital region; it stores body fluids (Jin Ye, 津液), and only through Qi transformation can they be excreted." The Qi of the Bladder travels via the Sanjiao (Triple Burner, 三焦), moves through the Couli (interstices of skin and muscle, 腠理), fills the muscles, and reaches the skin and hair to defend the exterior and maintain solidity. Yang Qi defends the exterior, preventing hundred pathogens from entering; thus its meridian is called the Taiyang (Greater Yang, 太阳) meridian. In cases of intense summer heat, hyperactive Yang steams and agitates the water Qi of the Bladder, causing it to surge and spread outward, resulting in sweat. This is akin to rain in nature: when Yang spreads and Yin harmonizes, there is naturally no disease. Sometimes, external contraction of Wind-Cold causes the skin and hair to become loose and open, leading to fever and sweating. This occurs because the Qi of the Taiyang meridian is afflicted by pathogens and cannot defend the exterior, allowing sweat to escape. Patients with Heat-Dampness diseases of the Heart, Stomach, Liver, or Spleen also experience sweating; this is like moist earth under humid heat, which can also evaporate into clouds and rain. There are also spontaneous sweats due to Yang collapse, caused by the leakage and loss of Primordial Yang (Yuan Yang, 元阳) in the Bladder and Kidney. Consequently, the Yin fluid Qi rushes and overflows, scattering without retention. Qi is transformed by Water, and Water is essentially Qi; Sweat is essentially Water. When Qi collapses and escapes outward, sweat results. Understanding this reveals that sweat originates from the Qi aspect, not the Blood aspect. However, although sweat comes from the Qi aspect, it is never unrelated to the Blood aspect. Therefore, Heat in the Blood aspect can also steam the fluid of the Qi aspect, causing night sweats (Dao Han, 盗汗). This is because Qi and Blood, Yin and Yang, originally root and inhabit each other. If Blood in the Yin aspect is abundant, the fluid-Yin of the Yang aspect naturally becomes sufficient; if the fluid-Yin of the Yang aspect is adequate to distribute and nourish, the Blood of the Yin aspect becomes more harmonious and moist, avoiding pathologies where Yang invades Yin. If the fluid-Yin of the Yang aspect is insufficient, it further injures the Yin of the Blood. Thus, in Shanghan (Cold Damage, 伤寒) disease, excessive sweating leads to deficiency vexation and insomnia because it simultaneously injures the Yin of the Blood aspect. The Heart governs the Blood aspect; when the Yin of the Blood aspect is injured, the Heart Qi becomes unsettled. In some Shanghan cases, resolution should occur through sweating, but if sweating does not occur, healing may happen through epistaxis (Nosebleed, 鼻衄). This type of nosebleed is named "Red Sweat" (Hong Han, 红汗). Pathogens in the Yang aspect should carry the fluid of the Yang aspect out through emission. Since they cannot exit outwardly, they attack the Blood of the Yin aspect and exit through the nose, hence named "Red Sweat." This is a verification of Yang pathogens invading the Yin aspect. Hence, ancients stated that when Yang invades Yin, vomiting and nosebleeds occur. Knowing that internal rebellion of Yang invading Yin causes vomiting and nosebleeds, one understands that external leakage of Yang invading Yin causes blood-sweat on the skin. Blood is the fluid of the Heart. Skin and hair are the exterior correspondence of the Lung. Treatment methods should clear Heart Fire; once Fire is cleared, Yang will not invade Yin. Simultaneously treat Lung Metal; once Lung is regulated, skin and hair will not leak. Use Liangxue Dihuang Tang (Cool Blood and Replenish Yin Decoction, 凉血地黄汤) added with Sangbaipi (Morus Alba Root Bark, 桑白皮), Digupi (Lycium Bark, 地骨皮), Chantui (Cicada Slough, 蝉蜕), Baihe (Lily Bulb, 百合), and Puhuang (Typha Pollen, 蒲黄). For Blood deficiency with severe Fire, use Danggui Liu Huang Tang (Angelica Six-Huang Decoction, 当归六黄汤). For Qi deficiency and low Blood, use Danggui Buxue Tang (Angelica Tonify Qi Decoction, 当归补血汤) added with Sangbaipi, Digupi, Danpi (Moutan Cortex, 牡丹皮), Chantui, Zonglutan (Livistona Stem Carbon, 棕榈炭), Huangqin (Scutellaria Root, 黄芩), and Qinpi (Ailanthus Bark, 秦皮). Externally, apply Duanshi San (Calcined Stone Powder, 锻石散). This imitates Zhang Zhongjing's method of using warm powder for unceasing sweating. Alternatively, Taohua San (Peach Blossom Powder, 桃花散) can be used.
Skin and hair are the exterior correspondence of the Lung. Since sweat emerges from the skin and hair, blood-sweat should be treated by regulating Lung Metal to consolidate the skin and hair. Ren Shen Qing Fei Tang (Ginseng Clear Lung Decoction, 人参清肺汤) added with Puhuang is most suitable. Blood is governed by the Liver. Hyperactive Liver Fire forces Blood to move recklessly; use Danggui Lujian Wan (Angelica and Wormwood Pill, 当归芦荟丸) to treat internally. Yu Jiayan treated a woman with amenorrhea and generalized sweating, attributing it to Heat in the Yin aspect leaking into the Yang aspect. He used this formula to break menstrual stasis, thereby stopping sweat with bitter-astringent properties. Since Sweat and Blood share the same source, if Liver Fire is extremely hyperactive causing blood-sweat, borrowing this formula is particularly appropriate.
Hyperactive Stomach Fire can also cause blood-sweat because the Stomach governs muscles; Heat steaming the muscles causes blood-sweat. Use Zhuye Shigao Tang (Bamboo Leaf and Gypsum Decoction, 竹叶石膏汤) added with Puhuang, Chantui, and Danpi. Xijiao Dihuang Tang (Rhinoceros Horn and Rehmannia Decoction, 犀角地黄汤) is also effective.
General Discussion: Sweat is the fluid of the Yang aspect; Blood is the fluid of the Yin aspect. Yin and Yang have no separation; Blood and Water are inherently inseparable. Thus, excessive sweating injures Blood; purgative therapy causing fluid loss injures Blood; Heat binding in the Bladder causes lower bleeding. These show Water pathology inseparable from Blood. Hematemesis and hemoptysis must involve Phlegm-Fluid; Blood deficiency causes thirst and lack of fluid generation; patients with blood loss often develop edema; Blood stasis transforming into Water also causes swelling. These show Blood pathology inseparable from Water. Therefore, patients with epistaxis should not undergo diaphoresis again, as Blood pathology implies Yin fluid is already deficient; diaphoresis would further injure Qi-fluid, causing Yang-fluid to become deficient. Furthermore, cases starting with edema followed by hematemesis are incurable, as Water pathology should not severely injure Blood. Observing Xiao Chai Hu Tang (Minor Bupleurum Decoction, 小柴胡汤) harmonizing fluids to treat Heat entering the Blood Chamber (Re Ru Xue Shi, 热入血室); observing Tao Ren Cheng Qi Tang (Peach Kernel and Cathartic Decoction, 桃仁承气汤) breaking Blood clots to treat dysuria—these all demonstrate treating Water to treat Blood, and treating Blood to treat Water. In the Lower Jiao, the Sea of Blood and the Bladder occupy the same location. In the Upper Jiao, the Lung governs Water pathways, and the Heart governs Blood vessels. On the exterior of the body, sweat exits via skin/hair, while Blood circulates via meridians. Yin and Yang are interconnected. I have detailed this in my "Discussion on Water, Fire, Blood, and Qi." One must deeply understand this principle to know that treating Blood and regulating Qi, adjusting Yin and harmonizing Yang, allows for versatile application.