太阳之为病。脉浮头项强痛而恶寒。是恶寒乃太阳病一定之证。始而恶寒。继且发热矣
。
其恶寒与发热相兼。非如寒热往来之热时自热。寒时自寒也。所谓身大热而不欲去衣者此也
。凡风寒客于营卫之中。而洒淅恶寒者。其脉必浮。浮为在表。故曰恶寒者表未解也。虽里
证悉具。而表未解。不可攻里。必俟外解已。乃可攻也。若太阳病传入阳明者。则恶寒将自
罢。即 汗出。而不恶寒。反恶热矣。此太阳病初起发热恶寒之大概也。恶寒属表者脉必
浮。其有不浮而沉者阴病也。经云。发热恶寒者。发于阳也。无热恶寒者。发于阴也。发于
阳者病在表。宜解表为主。发于阴者病在里。宜温里为主。若阴病而误发其汗。则阳亡之变
。顷刻即至矣。阴病恶寒。以手足温者易治。手足逆冷者难治。故经云。少阴病恶寒而蜷。
时
自烦。欲去衣被者可治。又曰。少阴病恶寒身蜷而利。手足逆冷者。不治。又曰少阴病下利
。若利止恶寒而蜷卧。手足温者可治。此其义也。
恶寒属表者。在未汗以前。是谓表实。若既发汗之后。当不恶寒矣。而反恶寒者。则又
不属
实而属虚。故经云。发汗病不解。反恶寒者。虚故也。芍药甘草附子汤主之。盖以芍药甘草
两和营卫。而必藉附子以温经。则同一恶寒。而未汗以前。与既汗以后。又各不同如此。
更有里热郁盛。致阳气不得宣泄。而外恶寒者。此即内经所谓诸病恶寒。皆属于火者是
也。
辛温发表。大属非宜。而表阳被遏。其脉又多沉。与阴病相似。而又不可误于温里。其外显
假寒。内实真热。一经误用。反掌生杀。其辨之之法。则不以脉辨而以证辨。盖风寒之邪。
未经入里。口中必和。此则口中先干。其舌上燥白如积粉。甚或兼黄黑色。胸膈痞满。不大
便。或下利如深酱色。其兼厉气者。口中必有秽气。此即热甚阳郁之候。治宜宣发伏邪。使里
气通而郁阳发。则恶寒自罢。反大热而烦渴矣。然热作之后。人皆信为热。而当恶寒时。鲜
有识其为热者。不可不细心体认也。
又有背恶寒者。夫恶寒则一身皆恶。何以止称背恶寒。内经云。人身之阴阳。腹为阴。
背为
阳。背者胸中之府。诸阳受气于胸中，而转行于背。阴寒之气盛。阳虚不足御之。则背为之
恶寒。经云。少阴病一二日口中和。其背恶寒者当灸之。附子汤主之。论中口中和三字。最
宜着眼。惟其口中和。故可放胆用附子。又或乘阴气不足阳气内陷入阴中。而不转行于背。
则背亦为之微恶寒。经云。伤寒无大热。口燥渴。心烦。背微恶寒。白虎加人参汤主
之。二者治法天渊。于何辨之。亦辨之于口之渴与不渴而已矣。
太阳病的主要表现为：脉象浮，头痛连及项部僵硬疼痛，并且怕冷。这说明怕冷是太阳病必然出现的症状。起初只是怕冷，随后就会发热。
这种怕冷与发热同时出现的情况，不同于寒热往来那种热的时候自然发热、冷的时候自然发冷的情况。这里指的是身体高热却不想脱去衣服的情形。凡是风寒邪气客居在营卫之间，导致身体洒淅恶寒的，其脉象必定是浮脉。浮脉主表证，所以说“怕冷说明表证未解”。即使里证全部具备，只要表证未解，就不可攻逐里实，必须等到表证解除后，才可以攻里。如果太阳病传入阳明经，那么怕冷症状自然会停止，出现汗出，不再怕冷，反而怕热了。这是太阳病初起时发热恶寒的大致情况。
怕冷属于表证的，脉象必定浮；如果不浮而沉，则是阴病。经文说：“发热且怕冷的，是发于阳经；不发热只怕冷的，是发于阴经。”发于阳经的病位在表，治疗应以解表为主；发于阴经的病位在里，治疗应以温里为主。如果是阴病却误用发汗法，那么阳气亡失的变证，顷刻间就会到来。阴病怕冷，如果手足温暖则容易治疗，如果手足逆冷则难治。所以经文说：“少阴病怕冷且身体蜷缩，但时常自觉心烦，想要去掉衣被的，可以治愈。”又说：“少阴病怕冷、身体蜷缩且伴有下利，手足逆冷的，属不治之症。”又说：“少阴病下利，如果下利停止，虽然怕冷且蜷卧，但手足温暖的，可以治愈。”这就是其中的道理。
怕冷属于表证的，在未发汗之前，称为表实证。如果已经发汗之后，应当不再怕冷了。如果反而还怕冷，那就不属于实证而属于虚证。所以经文说：“发汗后病不解，反而怕冷的，是因为虚。”应用芍药甘草附子汤主治。这是因为芍药和甘草能调和营卫，但必须借助附子来温通经脉。同样是怕冷，但在未发汗前与已发汗后，机理又各不相同如此。
还有因为里热郁结炽盛，导致阳气不能宣泄，从而在外表现为怕冷的情况。这正是《内经》所说的“各种疾病出现怕冷，大多归属于火（热）”的意思。此时使用辛温解表的方法非常不适宜。由于表阳被遏制，脉象又多现沉象，与阴病相似，但又不可误用温里法。这是外显假寒、内实真热的情况，一旦误用温药，生死只在反掌之间。辨别的方法是：不以脉象辨别，而以症状辨别。因为风寒邪气尚未入里，口中必然平和；而此证口中先觉干燥，舌苔白燥如积粉，甚至兼见黄黑色，胸膈痞闷胀满，大便秘结，或者下利如深酱色。如果兼夹厉气（疫毒），口中必有秽臭之气。这就是热甚阳郁的征候。治疗宜宣发伏邪，使里气通畅而郁闭的阳气得以发散，则怕冷自然停止，随后会出现大热、烦躁和口渴。然而热势发作之后，人们都相信这是热证，而在怕冷的时候，很少有人能识别出这是热证，不可不细心体察辨认。
又有仅背部怕冷的情况。既然说是怕冷，应该是一身都怕冷，为什么只称背部怕冷？《内经》说：人身之阴阳，腹部为阴，背部为阳。背部是胸中精气汇聚之所，诸阳之气受之于胸中，转而运行于背部。如果阴寒之气盛，阳气虚弱不足以抵御，则背部会感到怕冷。经文说：“少阴病一二日，口中平和，背部怕冷的，应当施灸，并用附子汤主治。”论中“口中平和”这四个字，最值得关注。正因为口中平和，所以可以放心大胆地使用附子。又或者因阴气不足，阳气内陷入阴中，而不能转行于背部，则背部也会轻微怕冷。经文说：“伤寒没有大热，口燥渴，心烦，背部轻微怕冷，用白虎加人参汤主治。”这两种治法天壤之别，如何辨别呢？也是通过辨别口中是否口渴来区分的。
The main manifestation of Taiyang disease (Disease of the Bladder and Small Intestine channels) is a floating pulse, stiffness and pain in the head and nape, and aversion to cold. This indicates that aversion to cold is a definitive symptom of Taiyang disease. Initially, there is only aversion to cold, which is subsequently followed by fever.
This simultaneous occurrence of aversion to cold and fever differs from alternating chills and fever, where one feels hot spontaneously during febrile periods and cold spontaneously during chilly periods. Here, it refers to the condition where the body has high fever yet the patient does not wish to remove clothing. Whenever wind-cold pathogens lodge within Ying (Nutritive) and Wei (Defensive) levels, causing shivering aversion to cold, the pulse must be floating. A floating pulse indicates a pathogenic process at the Exterior level; therefore, it is said that "aversion to cold signifies that the Exterior syndrome has not yet resolved." Even if Interior symptoms are fully present, as long as the Exterior syndrome remains unresolved, purgative treatment for the Interior should not be administered. One must wait until the Exterior is resolved before treating the Interior. If Taiyang disease transmits to Yangming disease (Disease of the Stomach and Large Intestine channels), the aversion to cold will cease spontaneously, accompanied by sweating, no longer aversion to cold, but rather aversion to heat. This outlines the general presentation of fever and aversion to cold at the onset of Taiyang disease.
Aversion to cold belonging to the Exterior level is characterized by a floating pulse. If the pulse is not floating but deep, it indicates a Yin disease. The Classic states: "Fever with aversion to cold indicates onset from Yang; absence of fever with aversion to cold indicates onset from Yin." Diseases originating from Yang are located at the Exterior, and treatment should primarily focus on releasing the Exterior. Diseases originating from Yin are located in the Interior, and treatment should primarily focus on warming the Interior. If a Yin disease is mistakenly treated with diaphoresis (sweating method), the variation of Yang collapse will occur instantaneously. In Yin disease with aversion to cold, if the hands and feet are warm, it is easy to treat; if the hands and feet are cold (reversal cold), it is difficult to treat. Thus, the Classic states: "In Shaoyin disease (Disease of the Kidney and Heart channels) with aversion to cold and curling up, if the patient occasionally feels vexed and desires to remove clothing and bedding, it is curable." It also states: "In Shaoyin disease with aversion to cold, curling up, and diarrhea, if the hands and feet are reversal cold, it is incurable." It further states: "In Shaoyin disease with diarrhea, if the diarrhea stops, and although there is aversion to cold and curling up, the hands and feet are warm, it is curable." This explains the principle.
Aversion to cold belonging to the Exterior level, prior to sweating, is termed an Exterior Excess syndrome. After sweating has been induced, aversion to cold should cease. If aversion to cold persists or returns after sweating, it does not belong to Excess but to Deficiency. Thus, the Classic states: "After sweating, if the disease does not resolve and aversion to cold returns, it is due to Deficiency." The formula Shaoyao Gancao Fuzi Tang (Peony, Licorice, and Aconite Decoction) is indicated. This is because Shaoyao (Paeoniae Radix Alba) and Gancao (Glycyrrhizae Radix et Rhizoma) harmonize Ying and Wei, but they rely on Fuzi (Aconiti Lateralis Radix Praeparata) to warm the meridians. Thus, although the symptom is the same (aversion to cold), the pathology differs significantly between pre-sweating and post-sweating stages.
There is also a condition where excessive interior heat stagnation prevents the dissemination of Yang Qi, resulting in external aversion to cold. This corresponds to the statement in the *Neijing* (Inner Canon): "All diseases presenting with aversion to cold mostly belong to Fire (Heat)." In such cases, using acrid-warm exterior-releasing methods is highly inappropriate. Because the Exterior Yang is constrained, the pulse often appears deep, resembling Yin disease, yet it must not be mistaken for a case requiring warming the Interior. This presents as false cold externally but true heat internally. Misapplication of warming agents can lead to death instantly. The method of differentiation relies not on the pulse but on clinical signs. Since wind-cold pathogens have not entered the Interior, the mouth typically feels normal. In contrast, this condition presents with initial dryness in the mouth. The tongue coating may be dry and white like accumulated powder, or even yellowish-black. There may be chest and diaphragm fullness and obstruction, constipation, or diarrhea with dark soy-sauce-colored stool. If accompanied by pestilential qi (epidemic toxins), the breath will have a foul odor. These are signs of severe heat and Yang constraint. Treatment should aim to vent latent pathogens, allowing Interior Qi to flow freely and constrained Yang to disperse. Consequently, aversion to cold will cease, followed by high fever, vexation, and thirst. However, once the heat erupts, people readily recognize it as heat; few can identify it as heat during the phase of aversion to cold. Careful observation is essential.
There is also a condition of isolated aversion to cold in the back. If one speaks of aversion to cold, it usually affects the whole body; why specify only the back? The *Neijing* states: "In the human body, the abdomen is Yin, and the back is Yang. The back is the mansion of the Chest organs. All Yang Qi receives energy from the Chest and circulates through the Back." When Yin-cold Qi is excessive and Yang Qi is insufficient to resist it, the back feels cold. The Classic states: "In Shaoyin disease, within one or two days, if the mouth feels normal and there is aversion to cold in the back, moxibustion should be applied, and Fuzi Tang (Aconite Decoction) should be administered." The phrase "mouth feels normal" in the commentary is crucial. Precisely because the mouth is normal, one can confidently use Fuzi. Alternatively, due to insufficiency of Yin Qi, Yang Qi may sink inward into the Yin level and fail to circulate through the back, causing slight aversion to cold in the back. The Classic states: "In Shanghan (Cold Damage) without significant fever, with dry mouth and thirst, mental restlessness, and slight aversion to cold in the back, Baihu Jia Renshen Tang (White Tiger Decoction plus Ginseng) should be administered." The therapeutic approaches for these two conditions are worlds apart. How to differentiate them? By distinguishing whether there is thirst in the mouth or not.