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生姜，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，若泻而兼喘，复见闷乱摇头者，凶。
麻疹现后大便下脓血，或因泄泻而变成脓血者，或径自利者，但看疹疮出多而色红又多嗽者，只宜表疹，
俟其收后方宜解毒，兼治其利。
疹之初起最忌泄泻，然亦有始终泄泻而不妨者，禀之强弱异也，若因泻而嗽减变为喘者，则危矣，详前喘嗽条。
身热烦渴泄泻者，柴苓汤四苓散，如热甚或夏月益元散。
疹后作利，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。若昼夜有二三十次渐减至二三次，或渐多嗽，右手一指脉
渐起，清涕复来者，方可望生。若利变煤尘色，或现房漏色，或如青菜色，肛门如直筒，喘促
音哑，食饮不进，午后腮红，皆不治之证。
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？盖古人泄泻为热者什九，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，率由脾
胃之弱。若但知清火解毒，则脾土日败，而渐现房漏菜青色及气促绝食不治之证矣。病而
至此岂犹热耶，总属误耳。（德按∶马元仪曰暴病则多实，久病则多虚，滑脱者多寒，涩滞者
多热，参之脉证百无一失）故凡治泄泻者，即虽是疹，亦必察其有无热邪，故无热证热脉，
即当于痘疮泄泻条中求法治之。庶最危者，犹可望其生也，如余于诸法之外，而独言其要者有如此。
凡是麻疹初起时出现发热、呕吐和腹泻，这纯粹是热证，不能当作寒证来论述。这是因为火邪向内逼迫，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、生姜；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。
凡是麻疹发出后一两天或三四天，突然发生严重腹泻且咳嗽增多，应当使用升提透表的药物，配合分利湿浊的方法治疗。如果腹泻兼有气喘，又出现烦躁不安、摇头等症状，预后凶险。
麻疹显现后大便排出脓血，或者因为泄泻而变成脓血，或者自行腹泻，只要看疹疮出得较多且颜色红赤，并且咳嗽较多的，只适宜采用透发疹毒的方法，等到疹子收没之后，才适宜清热解毒，同时治疗腹泻。
麻疹初起最忌讳出现泄泻，然而也有始终泄泻而不妨碍预后的，这是因为患者体质强弱不同所致。如果因为腹泻导致咳嗽减轻却转变为气喘的，那就危险了，详见前文关于喘嗽的条目。
身体发热、心烦口渴、腹泻的，用柴苓汤或四苓散；如果热势很盛或者是夏季，可用益元散。
麻疹消退后出现腹泻，也有观察手指、咬指甲、撕扯口唇皮肤以及咬人等症状的，应当用解毒分利的药物治疗。如果排出的粪便中稠厚涎沫与红白相间的物质混杂，务必使用解毒的药物。如果昼夜腹泻二三十次，逐渐减少到两三次，或者咳嗽逐渐增多，右手食指脉象逐渐显现，清鼻涕再次流出的，才可以期望生存。如果排泄物变为煤尘色，或者呈现房漏（陈旧性结核溃破）的颜色，或者像青菜色，肛门松弛如直筒状，气喘急促、声音嘶哑，饮食不进，午后两腮发红，这些都是不治之证。
张景岳说：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，偶尔也有存在。而在泄泻这一病症上，这种情况尤为严重。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，却不知道凡是泄泻大多属于脾肾虚寒。就拿出疹这一病症来说，虽然有的由疹毒引起腹泻，但如果确实是实热证，大多不会导致腹泻，那些导致腹泻的，大率都是由脾胃虚弱引起的。如果只知道清热泻火解毒，那么脾胃之气就会日渐败坏，从而逐渐出现房漏、菜青色便以及气促绝食等不治之证。病情到了这种地步，难道还是热证吗？总归是误诊罢了。（德按：马元仪说暴病多实证，久病多虚证，滑脱不禁的多属寒证，涩滞不畅的多属热证，结合脉象和症状参详，几乎不会出错）所以凡是治疗泄泻的人，即使是在出疹的情况下，也必须考察是否有热邪。如果没有热证和热脉，就应当在痘疮泄泻的条目中寻找治疗方法。这样即使是极其危险的病例，还有希望存活，像我除了各种方法之外，特别强调要点的原因就在于此。
When measles first appear with fever, vomiting, and diarrhea, it is purely a heat syndrome and should not be treated as a cold syndrome. This is due to fire pathogen forcing inward: affecting the Upper Jiao (Upper Burner) leads to frequent vomiting; affecting the Lower Jiao (Lower Burner) leads to frequent diarrhea; affecting the Middle Jiao (Middle Burner) results in both vomiting and diarrhea. For pure diarrhea, Huangqin Tang (Scutellaria Decoction) is appropriate. For simultaneous vomiting and diarrhea, Huangqin Tang added with Banxia (Pinellia Rhizome) and Shengjiang (Fresh Ginger) is appropriate. For pure diarrhea accompanied by tenesmus (urgency and straining with little discharge), Lianhuang Jiedu Tang (Coptis Detoxification Decoction) combined with Yiyuan San (Benefit Prime Powder) is appropriate.
If one or two days, or three to four days after the eruption of measles, sudden severe diarrhea occurs with increased coughing, treatment should involve herbs that lift and vent the exterior, combined with methods to separate turbidity and promote urination. If diarrhea is accompanied by wheezing, along with restlessness and head-shaking, the prognosis is ominous.
After the manifestation of measles, if pus and blood appear in the stool, or if diarrhea transforms into pus and blood, or if there is spontaneous diarrhea, provided the rash is abundant and red in color and accompanied by significant coughing, only the method of venting the rash should be employed. Only after the rash has subsided should detoxification be applied, while simultaneously treating the diarrhea.
Diarrhea is most contraindicated at the initial stage of measles. However, there are cases where diarrhea persists throughout without hindering recovery, depending on the strength of the patient's constitution. If diarrhea causes the cough to subside but transforms into wheezing, the condition becomes critical; see the section on wheezing and coughing for details.
For symptoms of body heat, irritability, thirst, and diarrhea, Chai Ling Tang (Bupleurum and Poria Decoction) or Siling San (Four-Poria Powder) may be used. If the heat is severe or during summer months, Yiyuan San (Benefit Prime Powder) is suitable.
After measles recede, diarrhea may present with signs such as observing hands, biting nails, tearing lip skin, or biting others. These should be treated with drugs that detoxify and separate turbidity. If the discharge consists of thick saliva mixed with red and white substances, detoxifying drugs must definitely be used. If diarrhea occurs twenty to thirty times a day and night, gradually decreasing to two or three times, or if coughing gradually increases, the pulse at the first finger of the right hand gradually becomes palpable, and clear nasal discharge returns, survival can be hoped for. If the excrement turns the color of coal dust, the color of old tubercular ulcers (fanglou), or the color of green vegetables; if the anus becomes flaccid like a straight tube; if there is rapid breathing, hoarseness, inability to eat or drink, and redness of the cheeks in the afternoon, these are all incurable conditions.
Zhang Jingyue stated: In ancient medical texts, there are occasionally instances where explanations are incomplete or treatments are inappropriate. This is particularly true regarding diarrhea. Why? Because ancients believed nine-tenths of diarrhea cases were heat-related, thus often using Liu Hejian’s Huangqin Shaoyao Tang (Scutellaria and Peony Decoction) as the primary treatment, unaware that most diarrhea stems from Spleen and Kidney deficiency-cold. Taking measles as an example, although some diarrhea is caused by measles toxin, genuine excess-heat syndromes rarely cause diarrhea. Those that do cause diarrhea are mostly due to Spleen and Stomach weakness. If one only knows how to clear fire and detoxify, the Spleen and Stomach earth will deteriorate daily, gradually leading to incurable conditions such as fanglou, vegetable-green stools, shortness of breath, and cessation of food intake. At this stage, is it still a heat syndrome? It is entirely a misdiagnosis. (De notes: Ma Yuanyi said acute diseases are mostly excess, chronic diseases are mostly deficiency, incontinence is mostly cold, and stagnation is mostly heat. Combining pulse and symptom analysis yields near-perfect accuracy.) Therefore, when treating diarrhea, even in the context of measles, one must examine whether heat pathogen exists. If there are no heat signs or heat pulses, one should seek treatment methods from the section on chickenpox/measles-related diarrhea. Thus, even the most critical cases may have hope for survival. This is why I emphasize these key points beyond other methods.