头汗总为邪热上壅，而阳气内脱者间或有之。头为诸阳之会，三阴经不上头，故无头汗，所以
头汗属阳经。凡遍身有汗，谓之热越，若热不得越，而上蒸阳分，阳气上冲，津液上凑，故但头汗出
也。其兼症如太阳之热结在里，阳明之被火劫，与邪在半表半里之往来寒热，及热入血室，与虚烦
水结胸，发黄蓄血等症，俱是热不得越。治法，或散或和解，或清或下，除其邪而病自愈。至气脱
头汗，则多以妄
下伤阴，或克伐太过，或泄泻不止，以致阴竭于下，阳脱于上，小水不通，而上见头汗，则大危
矣。《活人》以头汗出者慎下，而张景岳治头汗条，有用承气者，始阅之，疑其相背，细看始知
其皆是也。《活人》之慎下，指五脏干枯，胞中空虚，津液少者而言。景岳则以便结腹胀痛，而
头汗者，宜承气以下之也。视头汗之兼症，而下与否殊施耳。至于有表邪，脉紧数，而头汗当散
者，宜小柴胡及诸柴胡饮。（见《景岳全书》新方散阵中。）有火邪，脉洪滑，内多烦热，而头
汗当清者，宜白虎汤、益元散之类，此治头汗之大概也。
睡则卫气行于里，内有伏热，其在表之阳气不密，故津液得泄，热蒸于外，腠理开而盗汗出。
醒则气行于表，而盗汗止矣。杂病盗汗，责在阴虚；瘟疫盗汗，总邪在三阳所致。三阳经俱有盗
汗，而邪在半表半里者居多，故总以和解为治。观仲景论三阳合病之盗汗，而归重于但欲眠睡，
热在胆经可知矣，小柴胡汤主之。
头汗总体上是由于邪热上壅所致，而阳气内脱的情况偶尔也有。头部是诸阳经汇聚的地方，三阴经不上达头部，所以不会出现头汗，因此头汗属于阳经病变。凡是全身出汗的，称为“热越”（热邪向外发散），如果热邪不能向外发散，而是向上蒸腾于阳分，导致阳气上冲，津液随之上聚，所以只有头部出汗。其伴随症状如太阳病的热结在里、阳明病被火法劫迫，以及邪在半表半里的往来寒热，还有热入血室、虚烦、水结胸、发黄、蓄血等病症，都是热邪不得外越的表现。治疗方法，或疏散、或和解、或清热、或攻下，去除邪气后疾病自然痊愈。至于气脱引起的头汗，多是因为误用泻下法损伤阴液，或者攻伐太过，或者泄泻不止，导致阴液枯竭于下，阳气脱失于上，小便不通，而上部出现头汗，这就非常危险了。《活人书》认为头汗出者慎用攻下法，而张景岳治疗头汗的条目中，有用承气汤的情况，初看觉得矛盾，仔细研读后才明白两者都是正确的。《活人书》所说的慎用攻下，是指五脏干枯、胞宫空虚、津液少的人而言。张景岳则是针对大便干结、腹胀痛且伴有头汗的人，适宜用承气汤来攻下。根据头汗的伴随症状不同，决定使用攻下法与否，施治方法截然不同。至于有表邪，脉象紧数，应当用疏散法的头汗，适宜用小柴胡汤及各类柴胡剂。（见《景岳全书》新方散阵中。）如果有火邪，脉象洪滑，体内多有烦热，应当用清热法的头汗，适宜用白虎汤、益元散之类，这是治疗头汗的大致原则。
睡眠时卫气行于体内，内有伏热，体表的阳气不固密，所以津液得以泄露，热气蒸腾于外，腠理开泄而盗汗出。醒来时卫气行于体表，盗汗就停止了。杂病中的盗汗，责之于阴虚；瘟疫中的盗汗，总归是邪气在三阳经所致。三阳经都可能出现盗汗，但邪气在半表半里的情况居多，所以总以和解法为治疗原则。观察仲景论述三阳合病的盗汗，并归结重于只想睡觉，可知热在胆经，以小柴胡汤主治。
Head sweating is generally caused by the upward congestion of pathogenic heat, although cases of internal collapse of Yang Qi occasionally occur. The head is the meeting point of all Yang meridians; since the three Yin meridians do not ascend to the head, head sweating does not occur in Yin meridian diseases, thus head sweating belongs to Yang meridians. When sweat covers the whole body, it is called "Re Yue" (the dispersal of heat outward). If heat cannot disperse outward but instead steams upward into the Yang regions, causing Yang Qi to rush upward and body fluids to gather there, only the head sweats. Accompanying symptoms include heat binding internally as seen in Taiyang disease, fire coercion in Yangming disease, alternating chills and fever with pathogens half-exterior and half-interior, heat entering the blood chamber, empty irritability, fluid-binding chest fullness, jaundice, and blood stasis syndromes—all of which represent heat failing to disperse. Treatment methods involve either dispersing, harmonizing, clearing heat, or purging to eliminate the pathogen, after which the disease resolves spontaneously. In cases of head sweating due to Qi collapse, it is often caused by improper purging injuring Yin, excessive attacking methods, or continuous diarrhea, leading to exhaustion of Yin below and collapse of Yang above. With no urination and head sweating appearing above, the condition is critical. *Huo Ren Shu* (Manual of Saving Lives) advises caution against purging when head sweating occurs, whereas Zhang Jingyue's treatment entries for head sweating include the use of Chengqi Tang. At first glance, these seem contradictory, but careful study reveals both are correct. The caution against purging in *Huo Ren Shu* refers to patients with dry viscera, empty bladder, and scant body fluids. Zhang Jingyue, however, addresses patients with constipation, abdominal distension and pain accompanied by head sweating, for whom purging with Chengqi Tang is appropriate. Thus, whether to purge depends on the accompanying symptoms of head sweating. For head sweating with exterior pathogens and tight, rapid pulse requiring dispersal, Xiaochaihu Tang and various Chaihu decoctions are suitable (see *Jingyue Quanshu*, New Formulas, Dispersing Formulas). For head sweating with fire pathogens, surging and slippery pulse, and internal irritability and heat requiring clearing, Baihu Tang and Yiyuan San are suitable. These constitute the general principles for treating head sweating.
During sleep, Wei Qi (Defensive Qi) travels inside. With latent heat within and insecure exterior Yang Qi, body fluids leak out. Heat steams outward, pores open, and night sweats occur. Upon waking, Wei Qi moves to the exterior, and night sweats cease. Night sweats in miscellaneous diseases are attributed to Yin deficiency; night sweats in epidemics are caused by pathogens affecting the three Yang meridians. All three Yang meridians can present with night sweats, but pathogens at the half-exterior/half-interior level are most common, so harmonization is the primary treatment principle. Observing Zhang Zhongjing’s discussion on night sweats in combined Three Yang diseases, where drowsiness is emphasized, indicates heat in the Gallbladder meridian, treated primarily with Xiaochaihu Tang.