凡寒热往来之病，其证有二∶盖一以外邪不解而然；一以阳盛阴虚而然。此其一为表证
，一为里证。所当辨治，不可紊也。
一、寒邪郁伏经络而为寒为热，此似疟非疟之类也。治法虽宜表散，然邪气得以久留者
，必其元气之虚而正不胜邪也。故凡治此者，皆当以兼补血气为主。若血分微虚，形气本不
甚弱，而邪有不解者，三柴胡饮。若火盛血燥而寒热不已者，一柴胡饮。若因劳倦，或气体
本弱，或肝脾不足，而邪有不净者，四柴胡饮，或五柴胡饮，或补中益气汤。若阳邪陷入阴
分，微兼内热，而邪有不解者，补阴益气煎。若脾胃阳气不健，中气不暖，而邪有不解者，
温胃饮。若病久元气大虚，而寒热不退者，但当单培元气，不必兼散，宜五福饮、归脾汤，
或大补元煎、理阴煎之类。察其阴阳，择而用之。若果阳虚，非用温补不可。
一、阴虚阳盛，或阴阳俱虚，而为寒热往来者。此以真阴不足，总属虚损之病也。然其
阴阳微甚，亦所当辨。如昼则热而夜则静者，此阳邪王于阴分，阳有余也。昼则静而夜则热
者，此阳邪陷入阴中，阴不足也。其有昼夜俱热，或兼烦躁多汗，而本非外感者。此证虽曰
重阳，而实则阴虚之极也。又有下见溏泄，或上见呕恶，而潮热夜热者，此元气无根，阳虚
之病也。大都阳实者，宜泻其阳，泻阳者。宜用苦寒。阴虚者，宜补其阴。补阴者，宜用甘
凉。惟阳虚一证，则身虽有热，大忌寒凉，此则人多不识也。然阴虚则病热，而阴气未竭者
，治之犹易；阳虚则病寒，而阳气未竭者，治之亦易。若孤阳无阴，而寒之不可，孤阴无阳
，而热之又不可，斯所谓两死之证也，无能为力矣。若阴虚阳盛而寒热往来，或夜热不止者
，加减一阴煎。若心经蕴热，火在阳分，而烦热往来者，二阴煎。若盗汗不止而夜热者，当
归六黄汤。若阴虚血热，崩淋不止而夜热者，保阴煎。若肝火不清，时多郁怒而为烦热者，
徙薪饮。若妇人多郁多怒，而寒热不止者，加味逍遥散。若三阴亏损，血虚火盛而烦热不止
者，地黄膏、三才封髓丹。若男、妇、小儿，凡脾胃受伤，阳虚火浮，而为潮热夜热者，必
用理阴煎，或温胃饮，或大补元煎之类，方可保全。此证最多，此治最妙，勿以此为奇谈也
。
凡是出现寒热往来症状的疾病，其证候主要有两种：一种是由于外邪未能解除所致；另一种是由于阳盛阴虚所致。前者属于表证，后者属于里证。对此应当仔细辨别并治疗，不可混淆。
一、寒邪郁结伏留于经络中，导致时而发冷时而发热，这类似于疟疾但并非疟疾的治疗方法虽然适宜使用解表发散法，但如果邪气能够长期停留体内，必定是因为元气虚弱，正气无法战胜邪气。因此，凡治疗此类病症，都应当以兼顾补益气血为主。如果血分轻微虚弱，形体和气息本来不很衰弱，而邪气仍未解除的，选用三柴胡饮。如果火势旺盛、血液干燥且寒热不止的，选用一柴胡饮。如果是由于劳累疲倦，或者体质原本虚弱，或者肝脾不足，而邪气未清干净的，选用四柴胡饮，或五柴胡饮，或补中益气汤。如果是阳邪陷入阴分，轻微兼有内热，而邪气未解除的，选用补阴益气煎。如果是脾胃阳气不健运，中焦之气不温暖，而邪气未解除的，选用温胃饮。如果病程长久导致元气大虚，而寒热不退的，只应当单纯培补元气，不必兼用发散之法，宜选用五福饮、归脾汤，或大补元煎、理阴煎之类。观察其阴阳虚实情况，选择适当的方法使用。如果确实是阳虚，非用温补方法不可。
二、阴虚阳盛，或者阴阳俱虚，而出现寒热往来的症状。这是由于真阴不足，总归属于虚损类的疾病。然而其中阴阳虚实的轻重程度，也应当加以辨别。例如白天发热而夜间安静的，这是阳邪在阴分旺盛，属于阳有余。白天安静而夜间发热的，这是阳邪陷入阴中，属于阴不足。如果有昼夜都发热，或者兼有烦躁多汗，而本来不是外感引起的。这种证候虽然称为重阳，但实际上是阴虚到了极点。又有下面出现腹泻，或者上面出现呕吐恶心，并且伴有潮热夜热的，这是元气无根，属于阳虚的病证。大体上，阳实证适宜泻其阳，泻阳的方法宜用苦寒药物。阴虚证适宜补其阴，补阴的方法宜用甘凉药物。只有阳虚这一证候，虽然身体有热象，但极其忌讳使用寒凉药物，这一点人们往往不能认识清楚。然而阴虚则生病热，而阴气尚未枯竭的，治疗还比较容易；阳虚则生寒，而阳气尚未枯竭的，治疗也比较容易。如果是孤阳没有阴依附，既不能用寒药，也不能用热药；孤阴没有阳依附，既不能用热药，也不能用寒药，这就是所谓的“两死”证候，无能为力了。如果是阴虚阳盛而寒热往来，或者夜间发热不止的，选用加减一阴煎。如果是心经蕴藏热邪，火在阳分，而烦热往来的，选用二阴煎。如果是盗汗不止且夜间发热的，选用当归六黄汤。如果是阴虚血热，崩漏淋沥不止且夜间发热的，选用保阴煎。如果是肝火不清除，时常多郁怒而导致烦热的，选用徙薪饮。如果是妇女多忧郁多愤怒，而寒热不止的，选用加味逍遥散。如果是三阴亏损，血虚火盛而烦热不止的，选用地黄膏、三才封髓丹。如果是男、女、小儿，凡是脾胃受伤，阳虚火浮，而出现潮热夜热的，必须使用理阴煎，或温胃饮，或大补元煎之类，才可以保全生命。这类证候最多，治疗方法最精妙，不要把它当作奇谈怪论。
In cases of alternating chills and fever, there are two main types of syndromes: one arises from the failure to resolve external pathogens; the other arises from excess Yang and deficiency of Yin. The former belongs to Exterior Syndromes (Biao Zheng), while the latter belongs to Interior Syndromes (Li Zheng). These must be distinguished and treated carefully without confusion.
1. When Cold Pathogens (Han Xie) stagnate and lodge in the meridians, causing alternating chills and fever, this resembles malaria but is not malaria. Although the treatment method should ideally involve releasing the exterior and dispersing pathogens, if the pathogenic factors remain for a long time, it is necessarily due to deficiency of Yuan Qi (Original Qi), where the healthy Qi cannot overcome the pathogenic Qi. Therefore, in treating such cases, the primary approach should be to simultaneously tonify Blood and Qi. If there is slight deficiency in the Blood aspect, and the physical constitution and Qi are not significantly weak, yet the pathogen remains unresolved, use San Chai Hu Yin (Three Bupleurum Decoction). If Fire is excessive and Blood is dry with persistent alternating chills and fever, use Yi Chai Hu Yin (One Bupleurum Decoction). If caused by fatigue or overwork, or if the constitution was originally weak, or if Liver and Spleen are insufficient, and the pathogen is not fully cleared, use Si Chai Hu Yin (Four Bupleurum Decoction), Wu Chai Hu Yin (Five Bupleurum Decoction), or Bu Zhong Yi Qi Tang (Tonify the Middle and Augment the Qi Decoction). If Yang pathogens have sunk into the Yin aspect, with slight internal heat and unresolved pathogen, use Bu Yin Yi Qi Jian (Decoction to Tonify Yin and Augment Qi). If Spleen and Stomach Yang Qi is not robust, and Middle Jiao Qi is not warm, with unresolved pathogen, use Wen Wei Yin (Warm the Stomach Decoction). If the disease has been prolonged leading to severe deficiency of Yuan Qi, with persistent chills and fever, one should solely focus on cultivating Yuan Qi without using dispersing methods; suitable formulas include Wu Fu Yin (Five Blessings Decoction), Gui Pi Tang (Restore the Spleen Decoction), Da Bu Yuan Jian (Greatly Tonify the Source Decoction), or Li Yin Jian (Regulate Yin Decoction). Observe the Yin and Yang conditions and select the appropriate treatment. If it is indeed Yang deficiency, warming and tonifying methods are indispensable.
2. Alternating chills and fever arising from Yin deficiency and Yang excess, or from simultaneous deficiency of both Yin and Yang, stem from insufficiency of True Yin (Zhen Yin) and generally belong to consumptive diseases. However, the degree of Yin and Yang deficiency or excess must also be distinguished. For instance, fever during the day and quietness at night indicates Yang pathogens flourishing in the Yin aspect, representing excess Yang. Quietness during the day and fever at night indicates Yang pathogens sinking into the Yin, representing deficiency of Yin. Cases where fever persists throughout the day and night, accompanied by irritability and profuse sweating, but which are not due to external contraction, although termed "Double Yang," are actually extreme Yin deficiency. Additionally, loose stools below or vomiting/nausea above, combined with tidal fever and night fever, indicate rootless Yuan Qi and belong to Yang deficiency diseases. Generally, for Yang Excess syndromes, one should purge the Yang, using bitter-cold herbs. For Yin Deficiency syndromes, one should tonify the Yin, using sweet-cool herbs. Only in the case of Yang deficiency, despite the presence of heat symptoms, cold and cooling methods are strictly contraindicated; this point is often unrecognized by many. However, when Yin deficiency causes heat, if Yin Qi is not exhausted, treatment is relatively easy; when Yang deficiency causes cold, if Yang Qi is not exhausted, treatment is also relatively easy. But if there is solitary Yang without Yin, neither cold nor hot treatments can be applied; if there is solitary Yin without Yang, neither hot nor cold treatments can be applied. This is referred to as a "double death" syndrome, for which there is no effective remedy. For Yin deficiency with Yang excess causing alternating chills and fever, or persistent night fever, use Jia Jian Yi Yin Jian (Modified One Yin Decoction). If Heart Meridian harbors heat, with Fire in the Yang aspect causing irritable alternating fever, use Er Yin Jian (Two Yin Decoction). If spontaneous night sweats persist with night fever, use Dang Gui Liu Huang Tang (Angelica Hexa-Huang Decoction). If Yin deficiency with Blood-Heat causes metrorrhagia and stranguria with night fever, use Bao Yin Jian (Preserve Yin Decoction). If Liver Fire is not cleared, leading to frequent depression and anger causing irritable fever, use Xi Xin Yin (Extinguish Fire Decoction). If women, prone to depression and anger, suffer from persistent alternating chills and fever, use Jia Wei Xiao Yao San (Modified Free and Easy Wanderer Powder). If the Three Yin channels are damaged, with Blood deficiency and Fire excess causing persistent irritable fever, use Di Huang Gao (Rehmannia Paste) or San Cai Feng Sui Dan (Three Talents Marrow-Sealing Pill). For men, women, and children, if Spleen and Stomach are injured, leading to Yang deficiency with floating Fire causing tidal fever and night fever, one must use Li Yin Jian, Wen Wei Yin, or Da Bu Yuan Jian to ensure preservation of life. Such cases are numerous, and the treatment principles are exquisite; do not dismiss them as eccentric theories.