凡疹子初起，发热吐利，纯是热证，不可作寒论。此乃火邪内逼上焦则多吐，下焦则多利，中
焦则吐利并作。自利者，宜黄芩汤。吐利者，宜黄芩汤加半夏二钱、生姜三片。自利里急后重，宜
黄连解毒汤合益元散。
凡疹出一二日，或三四日，忽然大泻，嗽多者，用升表之药，加以分利治之。苦泻而兼喘，复
见闷乱摇头者凶。
一、麻疹现后，大便下脓血，或因泄泻而变成脓血者，或径自利者，但看疮疹出多而色红又多嗽
者，只宜表疹。俟其收后，方宜解毒，兼治其痢。
一、疹子初起，最忌泄泻，然亦有始终泄泻而不妨者，禀之强弱异也。苦因泻嗽减而变为喘者则
危矣，详前喘嗽条。
一、身热烦渴泄泻者，柴苓汤、四苓散。如热甚或夏月，益元散。
一、疹后作痢、亦有看手咬指甲，撕口唇皮，及咬人等证，当以解毒分利药治之。若所下稠涎，
红白相兼者，务要用解毒之药。若昼夜由三、五十次，渐减至二、三次，成渐多嗽，右手一指脉渐
起，清涕复来者，方
可望生。若痢变煤色，或现房漏色，或如青菜色，肛门如筒，喘促音哑，饮食不进，午后腮红，皆
不治。
景岳曰∶自古方书，凡发挥未尽，及用治未当者，间亦有之，而惟于泄泻一证则尤其为最。何
也？盖古人以池泻为热者什九，故多用河间黄芩芍药汤为主治，而不知凡属泄泻，最多脾肾虚寒也
。即如出疹一证，虽有由疹毒而泻者，然果系实热，多不作泻，但致泻者，卒由脾胃之弱。若但知
清火解毒，则脾必日败，而渐现房漏、青菜色，及气促、绝食不治之证矣。病而至此，岂犹热耶？
总属误耳。故凡治泄泻者，即虽是疹，亦必察其有无热邪。如无热证热脉，即当于痘疮泄泻条求法
治之，庶最危者犹可望其生也。故余于诸法之外，而独言其要者有如此。
凡是疹子初起，出现发热、呕吐和腹泻，这纯粹是热证，不能当作寒证来论述。这是因为火邪内迫，如果影响上焦则多表现为呕吐，影响下焦则多表现为腹泻，影响中焦则呕吐和腹泻同时发生。如果是单纯腹泻，适宜用黄芩汤。如果呕吐和腹泻并见，适宜用黄芩汤加半夏二钱、生姜三片。如果是单纯腹泻且伴有腹部拘急疼痛、排便不爽（里急后重），适宜用黄连解毒汤合益元散。
凡是疹子发出后一两天，或三四天，突然发生严重腹泻，咳嗽较多时，使用升提透表的药物，配合分利小便的方法治疗。如果腹泻呈苦味（指泻下急迫臭秽）兼有气喘，又出现烦躁不安、摇头等症，预后凶险。
其一，麻疹显现后，大便排出脓血，或因泄泻而变成脓血的，或者自行腹泻的，只要看疮疹发出较多且颜色红赤，并且咳嗽较多的，只宜采用透发疹毒的方法。等到疹子收没之后，才适宜使用解毒药，兼治痢疾。
其二，疹子初起，最忌讳泄泻，但也有始终泄泻而不妨碍预后的，这是禀赋强弱不同的缘故。但如果因为腹泻导致咳嗽减轻却转变为气喘，那就危险了，详见前文“喘嗽”条。
其三，身体发热、心烦口渴、腹泻的，用柴苓汤、四苓散。如果热势很盛或者是夏季，用益元散。
其四，出疹后患痢疾，也有出现咬手指甲、撕扯口唇皮、咬人等症状的，应当用解毒分利的药物治疗。如果排出的粪便中有稠厚的涎沫，红白相间的，务必使用解毒的药物。如果昼夜腹泻三五十次，逐渐减少到两三次，同时咳嗽逐渐增多，右手食指脉象逐渐浮起，清鼻涕再次流出的，才有希望生存。如果痢疾变为煤黑色，或者呈现房漏色（暗红色），或者像青菜色，肛门松弛如筒状，气喘急促、声音嘶哑，饮食不进，午后两腮发红，都是不治之症。
张介宾说：自古以来的医书，凡是有发挥未尽之处，以及用药治疗不当的情况，偶尔也有，但在泄泻这一病症上尤其最为严重。为什么呢？大概古人认为泄泻属于热证的占十分之九，所以多用刘河间（刘完素）的黄芩芍药汤作为主治方剂，却不知道凡是属于泄泻，最多的是脾肾虚寒。就像出疹这一病症，虽然有的是由疹毒引起腹泻，但如果确实是实热证，大多不会导致腹泻，只有那些导致腹泻的，终究是因为脾胃虚弱。如果只知道清热泻火解毒，那么脾胃必定日益败坏，从而逐渐出现房漏色、青菜色，以及气促、绝食等不治之症。病情发展到这种地步，难道还是热证吗？总归是误诊罢了。所以凡是治疗泄泻的人，即使是在出疹的情况下，也必须观察是否有热邪。如果没有热证和热脉，就应当在痘疮泄泻的条目中寻找方法治疗，这样即使是危重的病例还有希望生存。所以我除了各种治疗方法之外，特别强调这些要点，原因就在于此。
Whenever the rash first appears, accompanied by fever, vomiting, and diarrhea, this is purely a heat syndrome and should not be interpreted as a cold syndrome. This occurs because fire pathogenic factors press inward: if they affect the Upper Jiao (Upper Burner), vomiting predominates; if they affect the Lower Jiao (Lower Burner), diarrhea predominates; if they affect the Middle Jiao (Middle Burner), both vomiting and diarrhea occur simultaneously. For cases of pure diarrhea, Huangqin Tang (Scutellaria Decoction) is appropriate. For cases with both vomiting and diarrhea, Huangqin Tang added with 2 qian of Banxia (Pinelliae Rhizoma) and 3 slices of Shengjiang (Zingiberis Rhizoma Recens) is appropriate. For cases of pure diarrhea accompanied by tenesmus (abdominal urgency and heavy sensation in the rectum), Lianhuang Jiedu Tang (Coptis Decoction for Resolving Toxic Heat) combined with Yiyuan San (Benefiting Primordial Powder) is appropriate.
When the rash has been present for one or two days, or three or four days, and suddenly severe diarrhea occurs with abundant coughing, treatment should employ herbs that lift and vent the exterior, combined with methods to separate clear from turbid fluids (promote urination to stop diarrhea). If the diarrhea is acrid and accompanied by wheezing, and symptoms such as restlessness and head shaking reappear, the prognosis is ominous.
First, after the measles rash manifests, if pus and blood appear in the stool, or if diarrhea transforms into dysentery with pus and blood, or if there is spontaneous diarrhea, observe whether the lesions are numerous and red, and whether coughing is abundant. In such cases, only the method of venting the rash should be used. Only after the rash subsides should detoxifying herbs be employed to concurrently treat the dysentery.
Second, during the initial stage of the rash, diarrhea is most contraindicated; however, there are cases where diarrhea persists throughout without hindering recovery, due to differences in constitutional strength. However, if diarrhea causes the cough to subside but transforms into wheezing, the condition becomes critical. Refer to the previous section on "Wheezing and Coughing."
Third, for cases involving body heat, irritability, thirst, and diarrhea, Chailing Tang (Bupleurum and Poria Decoction) or Siling San (Four-Powder Dispersion) is indicated. If the heat is severe or it is summer, Yiyuan San (Benefiting Primordial Powder) is indicated.
Fourth, for dysentery occurring after the rash, or for symptoms such as biting fingernails, tearing lip skin, and biting others, treatment should use detoxifying and fluid-separating herbs. If the discharge consists of thick saliva mixed with red and white substances, detoxifying herbs must definitely be used. If defecation occurs thirty to fifty times a day and night, gradually decreasing to two or three times, while coughing gradually increases, the pulse at the first finger position of the right hand gradually rises, and clear nasal discharge returns, survival is possible. However, if the dysentery turns coal-black, or assumes the color of old blood clots, or resembles green vegetables, with the anus flaccid like a tube, rapid breathing, hoarseness, inability to eat, and redness of the cheeks in the afternoon, these are all incurable conditions.
Zhang Jiebin stated: Since ancient times, medical texts have occasionally contained incomplete explanations or inappropriate treatments, but this is particularly true regarding the syndrome of diarrhea. Why? Because ancients believed that nine out of ten cases of diarrhea were due to heat, thus often using Liu Hejian’s Huangqin Shaoyao Tang (Scutellaria and Peony Decoction) as the primary treatment. They did not realize that most cases of diarrhea are actually due to deficiency-cold of the Spleen and Kidney. Take the case of exanthems (rash diseases): although some diarrhea is caused by rash toxins, if it is truly excess-heat, it rarely causes diarrhea. Diarrhea resulting from exanthems ultimately stems from Spleen-Stomach weakness. If one only knows how to clear fire and resolve toxicity, the Spleen will deteriorate daily, gradually leading to symptoms such as dark red discharge resembling old blood, green vegetable-like stool, shortness of breath, and anorexia—incurable conditions. When the disease reaches this stage, can it still be considered heat? It is entirely a misdiagnosis. Therefore, when treating diarrhea, even in the context of exanthems, one must examine whether there is any heat pathogen. If there are no heat signs or heat pulses, one should seek treatment methods from the section on "Diarrhea in Smallpox/Chickenpox," so that even critically ill patients may have hope for survival. Thus, among various methods, I emphasize these key points as follows.