寒热往来者。主半表半里。其病属少阳。盖少阳当阴阳出入之枢。邪至其地。与正气相
争。相
争则寒。争胜则热矣。此与恶寒发热有别。恶寒发热者。寒热互见。此则寒时自寒而不见热
。热时自热而不见寒也。又与寒热如疟者有别。寒热如疟者。作止有时。此则寒已而热。热
已而寒。一日三五发。甚者十数套。与疟状有以异也。小柴胡汤专治往来寒热。盖以柴胡治
半表。半夏治半里。黄芩生姜交除寒热。而加以人参甘枣扶正逐邪。盖病至少阳。发汗攻
里。皆所不宜。故以是为和解之剂。乃少阳病之定法也。
小柴胡汤主治往来寒热。人皆知之。此特半表证。而半里证。人多忽焉不讲。所谓半里
者。如
口苦心烦喜呕胸胁满痛之类是也。凡邪从太阳而来。其人仍发热。而少阳半里证已见。虽未
往
来寒热。即当从少阳和解。如经云。伤寒四五日。身热。恶风。颈项强。胁下满。手足温。
而渴者。小柴胡汤主之。又云。伤寒后六七日。发热。微恶寒。支节烦疼。心下支结。外证
未去者。柴胡桂枝汤主之是也。至少阳病。来路自太阳。而其去则入阳明之府。其来自太
阳者。如经云。伤寒五六日已发汗而复下之。胁满微结。小便不利。渴而不呕。往来寒热心
烦者。
此为未解也。柴胡桂枝干姜汤主之是也。其欲入府而犹未入者。如经云。伤寒十余日。热结
在里。复往来寒热者。与大柴胡汤是也。
寒热往来。属半表半里证。然有由表而里者。又有由里而表者。不可不辨也。大凡风寒
之邪
。多自表而里。湿热之邪。多自里而表。风寒法。仲景论中详矣。至湿热之邪。伏于募原。
其起病即见呕渴。胸腹满。不大便诸里证。及其发热。往往热已而寒。寒已而热。此其里证
重于表证。宜察其里证之轻重。使里先和。则表自解。盖病自里而表。少
阳正当往来出入之界。故其始往来寒热。继则热多寒少。再则但热不寒。至昼夜壮热。而谵
妄烦渴毕见。此病之由轻入重也。至于由重出轻。则必使谵妄烦渴诸里证先罢。身热渐和。
其时邪气已退。正气未复。又复相争而为往来寒热。此乃病出入之大机。而前之寒热往来为
病进。后之寒热往来为病退。总视其里证之轻重有无为据也。其有邪气全退。表里俱和。而
仍寒热未去。往来如疟者。此因正气未复。宜调其饮食。和其营卫。自然渐愈。切不可骤与
峻补。恐余邪为恋。反增其害矣。
又伤寒往来寒热。与疟相似而实非。凡疟当未作之时。饮啖如平人。至疟作而始作。此
则默默不欲饮食。兼有口苦心烦喜呕胸胁痛诸里证。以此为辨。
Alternating chills and fever (alternating episodes of cold and heat) indicates a pathogenic location at the half-exterior and half-interior level. This pathology belongs to the Shaoyang (Lesser Yang) channel. The Shaoyang serves as the pivot for the entry and exit of Yin and Yang. When pathogens reach this region, they contend with healthy Qi. Contention manifests as chills, while the victory of healthy Qi over pathogens manifests as fever. This differs from simultaneous aversion to cold and fever; in simultaneous aversion to cold and fever, both sensations occur concurrently. In alternating chills and fever, one feels only cold without fever during the chill phase, and only heat without chills during the fever phase.
This also differs from "chills and fever resembling malaria." Malaria-like chills and fever have regular intervals of onset and cessation. Alternating chills and fever involve cycles of cold followed by heat, or heat followed by cold, occurring three to five times a day, or even more than ten times in severe cases, which distinguishes it from malaria. Xiao Chai Hu Tang (Minor Bupleurum Decoction) is specifically indicated for alternating chills and fever. Bupleuri Radix (Chaihu) treats the half-exterior aspect, Pinelliae Rhizoma Preparatum (Banxia) treats the half-interior aspect, Scutellariae Radix (Huangqin) and Zingiberis Recens Rhizoma (Shengjiang) jointly resolve cold and heat, while Ginseng Radix et Rhizoma (Renshen), Glycyrrhizae Radix et Rhizoma (Gancao), and Jujubae Fructus (Dazao) support healthy Qi to expel pathogens. Once the disease reaches the Shaoyang stage, diaphoresis (sweating methods) and purgation are contraindicated. Therefore, Xiao Chai Hu Tang is used as a harmonizing formula, representing the standard treatment method for Shaoyang diseases.
It is widely known that Xiao Chai Hu Tang treats alternating chills and fever, but this primarily addresses the half-exterior syndrome. The half-interior syndrome is often neglected. The half-interior syndrome includes symptoms such as bitter taste in the mouth, irritability, frequent vomiting, and fullness/pain in the chest and hypochondrium. If pathogens transmit from the Taiyang (Greater Yang) channel, and the patient still has fever along with evident Shaoyang half-interior symptoms, even if alternating chills and fever have not yet appeared, treatment should follow the Shaoyang harmonizing principle. As stated in the classic text: "In Shanghan (Cold Damage) after four or five days, if there is body heat, aversion to wind, stiffness of the neck and nape, fullness below the costal margin, warmth of the hands and feet, and thirst, Xiao Chai Hu Tang should be administered." It also states: "After Shanghan, six or seven days later, if there is fever, slight aversion to cold, discomfort and pain in the joints, subcostal fullness/stagnation, and exterior symptoms persist, Chai Hu Gui Zhi Tang (Bupleurum and Cinnamon Twig Decoction) should be administered."
Regarding Shaoyang disease, its origin is from the Taiyang channel, but its progression may enter the Yangming Fu organs. Cases originating from Taiyang include: "After five or six days of Shanghan, if sweating was performed followed by inappropriate purgation, resulting in fullness below the costal margin with slight stagnation, difficulty in urination, thirst without vomiting, and alternating chills and fever with irritability, this indicates unresolved pathogen. Chai Hu Gui Zhi Gan Jiang Tang (Bupleurum, Cinnamon Twig, and Dried Ginger Decoction) should be administered." Cases where the pathogen intends to enter the Fu organs but has not yet done so include: "After more than ten days of Shanghan, if heat is consolidated internally and alternating chills and fever recur, Da Chai Hu Tang (Major Bupleurum Decoction) should be administered."
Alternating chills and fever belong to the half-exterior and half-interior syndrome. However, one must distinguish between transmission from exterior to interior and from interior to exterior. Generally, Wind-Cold pathogens tend to transmit from the exterior to the interior, whereas Damp-Heat pathogens tend to emerge from the interior to the exterior. Zhang Zhongjing detailed the treatment principles for Wind-Cold in his treatises. Regarding Damp-Heat pathogens latent in the Mu Yuan (Membrane Source), the onset often presents with interior symptoms such as vomiting, thirst, abdominal fullness, and constipation. When fever occurs, it typically follows a pattern of heat then cold, or cold then heat. In such cases, interior symptoms outweigh exterior ones. One must assess the severity of interior symptoms; once the interior is harmonized, the exterior will resolve spontaneously. Since the disease moves from interior to exterior, passing through the Shaoyang pivot, the initial stage features alternating chills and fever, progressing to more heat than cold, then to heat without cold, eventually leading to sustained high fever throughout the day and night, accompanied by delirium, restlessness, and extreme thirst. This represents the progression from mild to severe.
Conversely, recovery from severe to mild requires the resolution of interior symptoms like delirium and thirst first, followed by the gradual calming of body heat. At this stage, pathogens have retreated, but healthy Qi has not yet recovered. Residual contention between healthy Qi and lingering pathogens causes alternating chills and fever. This marks the critical mechanism of disease movement: prior alternating chills and fever indicate disease progression, while subsequent occurrences indicate disease regression. The determination relies on the presence and severity of interior symptoms. If pathogens have completely cleared and the interior and exterior are harmonious, yet chills and fever resembling malaria persist, this is due to un-recovered healthy Qi. Treatment should focus on regulating diet and harmonizing Ying (Nutritive) and Wei (Defensive) Qi, leading to natural recovery. Sudden use of strong tonics must be avoided, as it may retain residual pathogens and exacerbate the condition.
Furthermore, alternating chills and fever in Shanghan resemble malaria but are fundamentally different. In malaria, patients eat and drink normally before an attack, with symptoms appearing only during the episode. In contrast, patients with Shanghan alternating chills and fever exhibit apathy, loss of appetite, and accompany their condition with interior symptoms such as bitter taste, irritability, vomiting, and chest/hypochondriac pain. These features serve as the basis for differentiation.