伤寒盗汗。何以明之。盗汗者。谓睡而汗出者也。自汗则不论睡与不睡。自然而出
也。及盗汗者。不睡则不能汗出。方其睡也。凑凑然出焉。觉则止而不复出矣。杂病
盗汗者。责其阳虚也。伤寒盗汗者。非若杂病之虚。是由邪气在半表半里使然也。
何者。若邪气一切在表干于卫。则自然汗出也。此则邪气侵行于里。外连于表邪。
及睡则卫气行于里。乘表中阳气不致。津液得泄。故但睡而汗出。觉则气散于表。
而汗止矣经曰。微盗汗出。反恶寒者。表未解也。又阳明病。当作里实。而脉浮者。云
必盗汗。是犹有表邪故也。又三阳合病。目合自汗。是知盗汗为邪气在半表半里
之间明矣。且自汗有为之虚者。有为之实者。其于盗汗之证。非若自汗有实者。悉
当和表而已。不可不知也。
伤寒头汗。何以明之。头者诸阳之会也。邪搏诸阳。津液上凑。则汗见于头也。邪热
内蓄。蒸发腠理。遍身汗出者。谓之热越。若身无汗。则热不得越。热蒸于阳。故但头
汗出也。何者。以三阴之经。皆上至颈胸中而还。不循于头。独诸阳脉上循于头尔。
经曰。但头汗出。身无汗。剂颈而还。小便不利。渴饮水浆。此为瘀热在里。身必发黄。
为热不得越而上达者也。又热入血室。与其虚烦。或阳明被火。及水结胸。皆但头
汗出也。俱是热郁于内。而不得越者也。此数者。或吐或下。皆欲除其热也。或谓头
汗之证。悉属阳明。而为里热也。而有不属阳明。属表者乎。且邪但在表者。则无头
汗之证。必也寒湿相搏。与邪气半在表半在里者。乃有头汗也。伤寒五六日。已发
汗而复下之。胸胁满微结。小便不利。渴而不呕。但头汗出。往来寒热心烦。及伤寒
五六日。头汗出。微恶寒。手足冷。心下满。口不欲食。大便硬。脉细者。皆邪气半在表
半在里。令头汗出也。湿家但头汗出。欲得被覆向火者。寒湿相搏。令头汗出也。兹
数者。皆邪气所干。令头额自然汗出。又不谓之逆。其小便不利。则恶见头汗出也。
湿家下后。亦恶见头汗出也。兹二者乃为头汗之逆者也。何则。以小便不利而成
关格。若头汗出阳脱也。经云。关格不通。不得尿。头无汗者生。有汗者死。湿家下后。
若额上汗出。而微喘者。亦阳脱也。经云。湿家下之。额上汗出。小便不利者死。下利
不止者亦死。脉经曰。阳气上出。汗见于头者。盖阳脱也。则知可治而治。知其不可
治而不治。皆得十全之上者。在于明辨而审也。
伤寒盗汗。如何阐明？所谓盗汗，是指睡着时出汗。自汗则不论睡着还是醒着，都会自然出汗。至于盗汗，不睡觉时不会出汗，等到睡着时，就悄悄地渗出来，醒来后就停止而不再出了。杂病中的盗汗，责之于阳气虚弱。伤寒中的盗汗，不像杂病那样是虚证，而是由邪气在半表半里之间所致。为什么呢？如果邪气完全在体表干扰卫气，就会自然出汗。这里是邪气侵入体内，外部连接着表邪，等到睡着时，卫气运行到体内，趁着表里阳气不相顺接，津液得以外泄，所以只是睡着时出汗，醒来后气散于体表，汗就停止了。《内经》说：“轻微盗汗出，反而恶寒的，说明表证未解。”又有阳明病，本应属于里实证，但如果脉象浮，就说一定会出现盗汗，这是因为还有表邪的缘故。又有三阳合病，眼睛闭合时自汗出，由此可知盗汗确实是邪气在半表半里之间的表现。况且自汗有因虚引起的，也有因实引起的。对于盗汗的证候，不像自汗有实证那样，只需调和表气即可，这一点不可不知道。
伤寒头汗。如何阐明？头部是诸阳经汇聚的地方。邪气搏结于诸阳经，津液向上涌聚，就会在头部出汗。邪热内蕴，蒸发腠理，导致全身出汗的，叫做“热越”（热邪向外发散）。如果身体没有汗，那么热邪就无法向外发散，热气蒸腾于阳经，所以只有头部出汗。为什么呢？因为三条阴经，都上行至颈部和胸部就返回了，不循行于头部。只有诸阳经才上行循行于头部。《内经》说：“只有头部出汗，身体无汗，汗止于颈部以下，小便不利，口渴想喝水浆，这是瘀热在体内，身体必定发黄。”这是因为热邪无法向外发散而上达所致。又有热入血室，以及虚烦，或者阳明病被误用火法治疗，以及水饮结胸，都只出现头部出汗。这些都是热邪郁结在内部而无法发散。这几种情况，有的用吐法，有的用下法，都是为了清除热邪。有人说头汗的证候，都属于阳明，是里热证。那有没有不属于阳明、属于表证的吗？况且邪气只在体表的，就不会有头汗的证候。一定是寒湿相互搏结，与邪气一半在表一半在里的情况，才会有头汗。伤寒五六天，已经发过汗又用了下法，出现胸胁胀满微结，小便不利，口渴但不呕吐，只有头部出汗，往来寒热，心烦。以及伤寒五六天，头部出汗，轻微恶寒，手脚冷，心下胀满，口不想吃东西，大便硬，脉细的，都是邪气一半在表一半在里，导致头部出汗。患有湿病的人只有头部出汗，想要盖被子靠近火源的，是寒湿相互搏结，导致头部出汗。这几种情况，都是邪气所干犯，导致额头自然出汗，又不称之为逆证。但是如果有小便不利，就厌恶见到头部出汗。湿病患者经过攻下治疗后，也厌恶见到头部出汗。这两种情况才是头汗的逆证。为什么呢？因为小便不利会导致关格（大小便不通），如果头部出汗，就是阳气脱失。《内经》说：“关格不通，不能排尿，头部无汗的能生，有汗的会死。”湿病患者经过攻下后，如果额头出汗且轻微气喘的，也是阳气脱失。《内经》说：“湿病患者被攻下后，额头出汗，小便不利的会死，腹泻不止的也会死。”《脉经》说：“阳气上越，汗见于头部，这是阳气脱失。”因此知道可以治疗的就去治疗，知道不可治疗的就不去治疗，都能达到十全的效果，关键在于明辨和审慎。
Shaoyin Dao Han (Night Sweats in Cold Damage). How is it explained? Dao Han (Night Sweats) refers to sweating that occurs during sleep. Zi Han (Spontaneous Sweating), on the other hand, occurs naturally regardless of whether one is sleeping or awake. As for Dao Han (Night Sweats), there is no sweating when not sleeping; only when asleep does it seep out quietly, and it stops upon waking without recurring. In miscellaneous diseases, Dao Han (Night Sweats) is attributed to Yang Qi Deficiency (Deficiency of Defensive and Warming Energy). However, Dao Han (Night Sweats) in Shanghan (Cold Damage) is not a deficiency syndrome like in miscellaneous diseases, but is caused by pathogenic factors located between the exterior and interior (Half-Exterior Half-Interior). Why is this? If pathogenic factors were entirely on the exterior affecting the Wei Qi (Defensive Energy), spontaneous sweating would occur. Here, the pathogenic factors have invaded inward while still connected to the exterior. When asleep, the Wei Qi (Defensive Energy) moves inward. Taking advantage of the disconnection between the exterior and interior Yang Qi, the body fluids are released. Thus, sweating occurs only during sleep. Upon waking, the Qi disperses to the exterior, and sweating ceases. The Classic says: "Slight night sweats accompanied by aversion to cold indicate that the exterior pattern has not yet resolved." Furthermore, in Yangming Disease (Disease of the Yang Brightness), which should be an Interior Excess pattern, if the pulse is floating, it is predicted that there will definitely be night sweats, because there is still exterior pathogenic factor. Also, in San Yang He Bing (Combined Disease of the Three Yang Channels), where eyes are closed and spontaneous sweating occurs, it is evident that night sweats signify pathogenic factors between the half-exterior and half-interior. Moreover, spontaneous sweating can be caused by deficiency or excess. Regarding night sweats, unlike spontaneous sweating which can be excess and treated merely by harmonizing the exterior, this distinction must not be overlooked.
Shanghan Tou Han (Head Sweating in Cold Damage). How is it explained? The head is the convergence point of all Yang channels. When pathogenic factors contend with the Yang channels, body fluids rush upward, resulting in sweating on the head. If internal accumulation of pathogenic heat evaporates the Cou Li (interstices and pores), causing sweating over the entire body, this is called Re Yue (Heat Dissipation). If there is no sweating on the body, the heat cannot dissipate outward. Instead, the heat steams upward along the Yang channels, resulting in sweating only on the head. Why? Because the three Yin channels ascend only to the neck and chest before returning, and do not circulate to the head. Only the Yang channels ascend to the head. The Classic says: "Sweating only on the head, with no sweating on the body, stopping at the neck, accompanied by dysuria and thirst for fluids, indicates Stagnant Heat in the Interior. The body will likely develop Jaundice (Yellowing of the Skin and Eyes)." This is because the heat cannot dissipate outward and instead rises. Other conditions such as Re Ru Xue Shi (Heat Entering the Blood Chamber), empty irritability, Yangming disease treated incorrectly with fire methods, and Shui Jie Xiong (Water Accumulation in the Chest) also present with sweating only on the head. All these cases involve internal heat stagnation that cannot dissipate. For these conditions, emesis or purgation may be used to eliminate the heat. Some argue that head sweating always belongs to Yangming and represents interior heat. Is there any case belonging to the exterior rather than Yangming? Generally, if pathogenic factors are solely on the exterior, head sweating does not occur. It occurs specifically when cold-dampness contends with each other, or when pathogenic factors are half-exterior and half-interior. For example, after five or six days of Shanghan (Cold Damage), if sweating was induced followed by purgation, symptoms may include distension and slight knotting in the chest and hypochondrium, dysuria, thirst without vomiting, sweating only on the head, alternating chills and fever, and irritability. Similarly, after five or six days of Shanghan (Cold Damage), if there is head sweating, slight aversion to cold, cold hands and feet, fullness below the heart, desire not to eat, hard stools, and a fine pulse, these indicate pathogenic factors half-exterior and half-interior causing head sweating. Patients with Dampness disorders who sweat only on the head and wish to cover themselves near fire suffer from cold-dampness contention causing head sweating. These cases involve pathogenic invasion causing natural sweating on the forehead and are not considered adverse signs. However, if accompanied by dysuria, head sweating is viewed unfavorably. Similarly, after purgation in dampness patients, head sweating is unfavorable. These two scenarios represent adverse head sweating. Why? Dysuria can lead to Guan Ge (Obstruction and Reversal, characterized by inability to urinate or defecate). If head sweating occurs, it indicates Yang Qi Collapse (Collapse of Vital Energy). The Classic states: "When Guan Ge (Obstruction and Reversal) blocks flow and urination is impossible, absence of head sweating indicates survival, while presence indicates death." After purgation in dampness patients, if sweating appears on the forehead accompanied by slight panting, it also indicates Yang Qi Collapse. The Classic states: "If dampness patients are purged, and forehead sweating occurs with dysuria, death ensues; if diarrhea persists, death also ensues." The Pulse Classic states: "When Yang Qi ascends abnormally and sweating appears on the head, it signifies Yang Qi Collapse." Therefore, knowing what is treatable allows for treatment, and knowing what is untreatable prevents futile intervention, leading to complete recovery. This depends on clear differentiation and careful judgment.