伤寒衄者。何以明之。鼻中血出者是也。杂病衄者。责热在里。伤寒衄者。责热在表。
何以言之。病源曰。心主血。肝藏血。肺主气。开窍于鼻。血得热则散。随气上从鼻中
出。则为衄。是杂病者。责在里热也。经曰。伤寒脉浮紧不发汗。因致衄者。宜麻黄汤。
伤寒不大便六七日。头痛有热者。与小承气汤。其小便清者。知不在里。仍在表也。
当须发汗。若头痛者必衄。宜桂枝汤。以此观之。是伤寒衄者。责其表热也。千金翼
曰。吐血有三种。一曰肺疽。二曰伤胃。三曰内衄。既吐血家谓之内衄。则其鼻中出
血者。可谓之外衄。是经络之血妄行也。经络热盛。阳气臃重。迫血妄行。出于鼻则为衄。
经曰。其人发烦目瞑。剧者必衄。衄乃解。所以然者。阳气重故也。又曰。阳盛则
欲衄。阴虚小便难。言衄为经中阳盛也。凡伤寒脉浮。鼻中燥口燥。但欲漱水。不欲
咽者。是欲衄也。经曰。阳明病口干鼻燥。能食者则衄。又有不应发汗而强发汗。因
致衄者。经曰。少阴病但厥无汗。而强发之。必动其血。未知从何道出。或从口鼻。或
从目出。是名下厥上竭。为难治是也。衄家难为邪热在经。而又不可发汗。经曰。衄
家不可发汗。发汗则额上陷。脉急紧。直视不能 。不得眠。前云桂枝汤麻黄汤治
衄者。非治衄也。即是发散经中邪气耳。若邪气不得发散。壅盛于经。逼迫于血。则
因致衄也。即非桂枝麻黄汤专治衄也。太阳病脉浮紧。发热身无汗。自衄者愈。是
经中之邪。随血而散则解矣。故知衄者。不待桂枝汤麻黄汤发散之也。衄者若但
头汗出。身无汗。及汗出不至足者死。黄帝又皆以为不治之疾。临病之际。审而治
之。则不失矣。
伤寒病中的鼻衄，该如何阐明呢？就是指出血从鼻腔流出的情况。杂病中的鼻衄，责在里有热邪；而伤寒病中的鼻衄，责在表有热邪。
为什么这样说呢？《病源》记载：心主司血液，肝贮藏血液，肺主司气机，其窍开于鼻。血液遇到热邪就会散乱，随着气机上逆，从鼻腔流出，这就形成了鼻衄。因此，杂病中的鼻衄，责任在于里热。《伤寒论》经文说：“伤寒脉象浮紧，应当发汗而未发汗，因而导致鼻衄的，适宜用麻黄汤。”又经文说：“伤寒病人六七天不大便，头痛且伴有发热，给予小承气汤。如果小便清长，就知道病邪不在里，仍在表，应当需要发汗。如果头痛，必定会发生鼻衄，适宜用桂枝汤。”由此看来，伤寒病中的鼻衄，责任在于表热。
《千金翼方》记载：吐血有三种类型。一是肺疽，二是伤胃，三是内衄。既然吐血的人被称为内衄，那么从鼻腔流出的血，就可以称为外衄，这是经络中的血液妄行所致。经络中热势亢盛，阳气壅滞沉重，逼迫血液妄行，出于鼻腔就形成鼻衄。经文说：“病人感到心烦、眼睛昏花，严重的必定发生鼻衄，鼻衄之后病邪才能解除。之所以这样，是因为阳气重盛的缘故。”又说：“阳热亢盛则想要鼻衄，阴虚则小便困难。”这是在说明鼻衄是经中阳热亢盛的表现。凡是伤寒脉象浮，鼻中干燥、口中燥渴，只想含水漱口而不想咽下的，这是将要发生鼻衄的先兆。经文说：“阳明病口干鼻燥，能进食的就会发生鼻衄。”又有不应当发汗却强行发汗，因而导致鼻衄的情况。经文说：“少阴病仅见四肢厥冷而无汗，如果强行发汗，必定扰动血液，不知道血液会从哪个通道流出，或者从口鼻出，或者从眼睛出，这叫做‘下厥上竭’，属于难治之症。”
患有鼻衄的人（衄家），往往因为邪热在经络之中，而且不可使用发汗法。经文说：“鼻衄患者不可发汗，如果发汗，会导致额部凹陷，脉搏紧急拘急，两眼直视不能闭合，无法入睡。”前面提到的桂枝汤和麻黄汤治疗鼻衄，并不是专门治疗鼻衄本身，而是为了发散经络中的邪气罢了。如果邪气不能被发散，壅盛于经络，逼迫血液，就会导致鼻衄。所以，桂枝汤和麻黄汤并非专门治疗鼻衄的药物。太阳病脉象浮紧，发热且身体无汗，如果自然发生鼻衄，疾病就会痊愈。这是因为经络中的邪气随着血液的排出而消散，从而得到解除。因此可知，鼻衄的发生，并不等待桂枝汤或麻黄汤的发散作用。如果鼻衄仅仅只有头部出汗，身体无汗，以及汗出不到足部的，预后不良，属死证。黄帝均将其视为不治之疾。临证之际，仔细审察并治疗，就不会失误了。
Nosebleed (Rhinitis hemorrhage) in Shaoyang disease. How should this be explained? It refers to the condition where blood flows from the nasal cavity. In miscellaneous diseases, nosebleed is attributed to heat in the interior; whereas in Cold Damage (Shanghan) disease, nosebleed is attributed to heat in the exterior.
Why is this so? The *Bing Yuan* states: The Heart governs blood, the Liver stores blood, and the Lung governs Qi, with its orifice opening at the nose. When blood encounters heat, it scatters and follows the ascending Qi out through the nose, resulting in nosebleed. Thus, for nosebleed in miscellaneous diseases, the cause lies in interior heat. The Classic states: "In Cold Damage, if the pulse is floating and tight, and sweating has not been induced, leading to nosebleed, Mahuang Tang (Ephedra Decoction) is appropriate." Another passage states: "In Cold Damage, if there is no bowel movement for six or seven days, accompanied by headache and fever, Xiaochengqi Tang (Minor Order the Yang Decoction) should be given. If the urine is clear, it indicates that the pathogen is not in the interior but remains in the exterior, and sweating should be induced. If there is a headache, nosebleed will likely occur, and Guizhi Tang (Cinnamon Twig Decoction) is appropriate." From this, we see that nosebleed in Cold Damage disease is attributed to exterior heat.
The *Qianjin Yi Fang* states: There are three types of hematemesis (vomiting blood). One is lung abscess (Fei Ju), two is stomach injury, and three is internal nosebleed (Nei Nu). Since those who vomit blood are termed as having internal nosebleed, those whose blood flows from the nose can be termed external nosebleed (Wai Nu), which is caused by the reckless flow of blood in the meridians and collaterals. When heat in the meridians and collaterals is excessive, and Yang Qi is congested and heavy, it forces blood to flow recklessly; when it exits through the nose, it becomes nosebleed. The Classic states: "If the patient feels vexation and eye dimness, severe cases will inevitably result in nosebleed, after which the disease resolves. This is because Yang Qi is heavy." It also states: "When Yang is excessive, nosebleed is desired; when Yin is deficient, urination is difficult." This explains that nosebleed is a manifestation of excessive Yang in the meridians. Generally, in Cold Damage, if the pulse is floating, the nose is dry, the mouth is parched, and the patient only wishes to rinse water in the mouth without swallowing, this indicates an impending nosebleed. The Classic states: "In Yangming disease, if the mouth is dry and the nose is parched, and the patient can eat, nosebleed will occur." Furthermore, if sweating is not indicated but is forcibly induced, leading to nosebleed, the Classic states: "In Shaoyin disease, if there is only cold extremities without sweat, and sweating is forcibly induced, blood will inevitably be disturbed. It is unknown from which channel it will exit; it may come from the mouth or nose, or from the eyes. This is called 'lower cold and upper exhaustion' (Xia Jue Shang Jie), which is a difficult-to-treat condition."
Patients prone to nosebleed (Nu Jia) often have pathogenic heat in the meridians and cannot undergo sweating therapy. The Classic states: "Patients prone to nosebleed must not be sweated. If sweated, the forehead will sink, the pulse will become tight and urgent, the eyes will stare fixedly without closing, and sleep will be impossible." The previously mentioned use of Guizhi Tang and Mahuang Tang for nosebleed is not specifically to treat the nosebleed itself, but to disperse pathogenic factors in the meridians. If pathogenic factors cannot be dispersed and become congested in the meridians, forcing the blood, nosebleed occurs. Therefore, Guizhi Tang and Mahuang Tang are not exclusively for treating nosebleed. In Taiyang disease, if the pulse is floating and tight, there is fever and no sweat on the body, and spontaneous nosebleed occurs, the disease heals. This is because the pathogen in the meridians dissipates with the blood, leading to resolution. Thus, it is known that nosebleed does not wait for the dispersing action of Guizhi Tang or Mahuang Tang. However, if nosebleed is accompanied only by sweating on the head, no sweat on the body, and sweat failing to reach the feet, the prognosis is fatal. The Yellow Emperor regarded these as incurable conditions. At the time of clinical practice, careful examination and treatment will prevent errors.