一为阳衰表虚
此《经》所谓阳虚则恶寒也。治宜姜、附、参 之类，助阳固表。又有痹气一
症。帝曰∶人身非衣寒也，中（指脏腑言）非有寒气也，寒从中生者何？岐伯曰∶是人多
痹气也，（寒湿之气凝闭于肌体。）阳气少，阴气多，故身寒如从水中出。此则阳衰而兼寒实者也。
一为阴乘阳位
上焦阳虚，下焦素有阴寒之气，发动乘虚上干，故恶寒也。
一为阳气郁陷
或酒食、痰血、水湿、疮毒，郁抑阳气于里，不达于表；或劳倦郁抑，中气下
陷，不能升发，则表虚而怯寒也。或发之，或吐之。（产后血瘀、乳胀皆能致之。）观邪塞上
焦不通，抑遏阳气，东垣用升阳益胃汤，丹溪用吐法，吐出湿痰，使阳气随吐升发，可见矣。
一为热盛气散
热盛于里，火能生风，冲突元气，气从火散，故凛凛而寒，甚则振颤，鼓颔咬
牙，战栗如伤神守，有以大承气汤（见大便不通）下之而愈者。此外假寒，而内真热之症
也。（此为阳盛格阴，与阴盛格阳相反。阳，指内热言；阴，指外寒言。内热外寒，两相格拒，所谓阳盛格阴也。）
一为肺被火刑
肺主皮毛，热则气张汗越，失其敛肃之权，腠理虚疏，不任风寒，故恶之。
上明恶寒之理。至内伤外感之辨，昼夜之分，详后。
一内外之辨
外感恶寒，虽近烈火不除；内伤恶寒，得就温暖则解。
一昼夜之分
夜寒者，阴气（即寒邪）。旺于阴分；（为里、为脏、为血。）昼寒者，阴邪加于阳分；昼夜俱
寒者，重阴也。（与《发热篇》热分昼夜条对看，更详味下条自明。）按阳虚则畏寒而恶阴，故旦安
而暮乱；（至夜则寒也。）阴虚则畏热而恶阳，故夜宁而朝争；（昼则热也。）此正虚之候也。阳
邪实者，遇阳而愈旺，故朝热而暮轻；阴邪实者，逢阴而更强，故夜寒而昼减；此
邪实之候也。阳虚而阴邪乘于阳分，则气行阳二十五度而病发，故日寒而夜息；阴
虚而阳邪陷于阴分（即血分也），则气行阴二十五度而病发，故夜热而昼凉；（观疟疾或日发，或
夜发，可见矣。）此正虚挟邪之候也。其有昼夜俱热甚者，为重阳无阴；昼夜俱寒甚者，
为重阴无阳；昼寒夜热者，为阴阳交错也。其有久病虚弱，无分昼夜，作止不时者，
以正气不能主持，而阴阳相乘，胜复无常也。（若壮实人初病见此，又为邪正相攻，不时扰动之故。
观伤寒少阳证往来寒热，初无定期可见矣。）
一、阳衰表虚
这是《黄帝内经》所说的阳气虚弱则怕冷的情况。治疗适宜用干姜、附子、人参之类的药物，以助益阳气、巩固肌表。还有一种痹气病症。黄帝问：人的身体并不是因为穿衣少而寒冷，体内（指脏腑）也没有寒气，为什么寒气会从内部产生？岐伯回答：这是因为此人多有痹气，（寒湿之气凝闭于肌体。）阳气少，阴气多，所以身体寒冷如同从水中出来一样。这属于阳气衰弱兼有寒实邪气的情况。
二、阴乘阳位
上焦阳气虚弱，下焦素有阴寒之气，发动后趁虚向上侵犯，从而导致怕冷。
三、阳气郁陷
或因饮酒饮食、痰浊瘀血、水湿、疮毒等，郁抑阳气于体内，不能通达于体表；或因劳累倦怠导致郁抑，中气下陷，不能升发，从而表现为表虚而怯冷。或者采用发散的方法，或者采用催吐的方法。（产后血瘀、乳房胀痛都能导致这种情况。）观察邪气堵塞上焦不通，抑制遏止阳气，李东垣使用升阳益胃汤，朱丹溪使用吐法，吐出湿痰，使阳气随着呕吐而升发，由此可见。
四、热盛气散
热气在体内炽盛，火能生风，冲击元气，气随火而散失，所以感到凛冽寒冷，严重时出现颤抖，鼓动脸颊，咬牙，战栗如同患神守病，有的用大承气汤（见大便不通章节）攻下而痊愈。这是外假寒、内真热的病症。（这是阳盛格阴，与阴盛格阳相反。阳，指内热而言；阴，指外寒而言。内热外寒，相互格拒，称为阳盛格阴。）
五、肺被火刑
肺主皮毛，受热则气张汗出，失去收敛肃降的权力，腠理虚疏，不能承受风寒，所以厌恶风寒。
以上阐明了恶寒的道理。至于内伤与外感的辨别，以及昼夜的区别，详见后文。
一、内外之辨
外感引起的恶寒，即使靠近烈火也不能消除；内伤引起的恶寒，得到温暖就能缓解。
二、昼夜之分
夜间发冷，是阴气（即寒邪）旺盛于阴分；（阴分指里、脏、血。）白天发冷，是阴邪加于阳分；昼夜都发冷，是重阴。（结合《发热篇》中热分昼夜的条目对照阅读，仔细体味下条自然明白。）按：阳气虚弱则畏寒而厌恶阴，所以早晨安和而傍晚混乱；（到了夜晚就寒冷。）阴气虚弱则畏热而厌恶阳，所以夜晚安宁而早晨争斗；（白天就发热。）这是正气虚弱的证候。阳邪实证者，遇到阳气则更加旺盛，所以早晨发热而傍晚减轻；阴邪实证者，遇到阴气则更加强盛，所以夜晚寒冷而白天减轻；这是邪气实证的证候。阳气虚弱而阴邪乘袭阳分，则气行于阳分二十五度时发病，所以白天寒冷而夜晚休息；阴气虚弱而阳邪陷入阴分（即血分），则气行于阴分二十五度时发病，所以夜晚发热而白天凉爽；（观察疟疾或白天发作，或夜晚发作，就可以明白了。）这是正气虚弱夹杂邪气的证候。其中有昼夜都严重发热的，为重阳无阴；昼夜都严重发冷的，为重阴无阳；白天冷晚上热的，为阴阳交错。其中有久病虚弱，不分昼夜，发作停止没有定时的，是因为正气不能主持，而阴阳相互乘袭，胜复无常。（如果是体质壮实的人初病见此症状，又是邪正相攻，不时扰动的缘故。观察伤寒少阳证的往来寒热，起初就没有定期，就可以明白了。）
1. Yang Deficiency and Exterior Deficiency
This refers to what the *Classic* (Huangdi Neijing) states: "When Yang is deficient, there is aversion to cold." Treatment should employ herbs such as Shengjiang (Zingiberis Rhizoma Recens), Fuzi (Aconiti Lateralis Radix Praeparata), and Renshen (Ginseng Radix et Rhizoma) to assist Yang and consolidate the exterior. There is also a condition known as Bi Qi (Obstructive Qi). The Yellow Emperor asked: "The human body is not cold due to lack of clothing, nor is there cold qi within the Zang-Fu organs; why does cold arise from within?" Qibo replied: "This person has much Bi Qi, (cold-damp qi congealing and obstructing the musculature.) Yang qi is scanty, Yin qi is abundant, thus the body feels cold as if emerging from water." This constitutes a case of Yang deficiency combined with excess cold pathogen.
2. Yin Encroaching upon Yang Position
When Yang qi in the Upper Jiao is deficient, Yin-cold qi previously existing in the Lower Jiao activates and invades upward taking advantage of the deficiency, resulting in aversion to cold.
3. Depression and Sinking of Yang Qi
Due to alcohol, food stagnation, phlegm-stasis, dampness-water, or sores-toxins, Yang qi is depressed internally and cannot reach the exterior; or due to fatigue and overwork causing depression, Middle Qi sinks and cannot ascend, leading to exterior deficiency and fear of cold. One may use dispersing methods or emetic methods. (Postpartum blood stasis and breast distension can both cause this.) Observing that pathogens block the Upper Jiao, inhibiting and suppressing Yang qi, Li Dongyuan used Shengyang Yiwang Tang (Ascending Yang and Benefiting Stomach Decoction), while Zhu Danxi used emesis to expel damp-phlegm, allowing Yang qi to ascend with the vomiting, which demonstrates this principle.
4. Excess Heat Scattering Qi
Heat is excessive internally; fire generates wind, assaulting Yuan Qi (Original Qi), causing Qi to scatter with the fire, resulting in shivering cold. In severe cases, tremors occur, cheeks puff out, teeth are clenched, and rigors resemble Shen Shou disease (a condition characterized by severe chills). Some cases are cured by purging with Dachengqi Tang (Major Order the Qi Decoction) when constipation is present. This is a condition of false cold externally and true heat internally. (This is Yang Excess Repelling Yin, opposite to Yin Excess Repelling Yang. 'Yang' here refers to internal heat; 'Yin' refers to external cold. Internal heat and external cold repel each other, termed Yang Excess Repelling Yin.)
5. Lung Punished by Fire
The Lung governs the skin and hair. When heated, Qi expands and sweat escapes, losing its astringent and descending authority. The Couli (pores) become loose and deficient, unable to withstand Wind-Cold, hence aversion to it.
The above clarifies the principles of aversion to cold. Regarding the differentiation between internal injury and external contraction, and the distinction between day and night, see below.
Differentiation between Interior and Exterior
Aversion to cold due to external contraction remains even when near intense fire; aversion to cold due to internal injury resolves with warmth.
Distinction between Day and Night
Cold at night indicates Yin qi (i.e., Cold Pathogen) flourishing in the Yin divisions. (Yin divisions refer to Interior, Zang organs, and Blood.) Cold during the day indicates Yin pathogen affecting the Yang divisions. Cold throughout day and night indicates Heavy Yin. (Compare with the section on fever distinguishing day and night in the *Fever Chapter*; careful study of the following clause will clarify.) According to theory: Yang deficiency leads to fear of cold and aversion to Yin, so one is peaceful in the morning but chaotic in the evening. (It becomes cold at night.) Yin deficiency leads to fear of heat and aversion to Yang, so one is peaceful at night but agitated in the morning. (It becomes hot during the day.) These are signs of Righteous Qi deficiency. Yang Excess pathogens flourish when encountering Yang, so heat is worse in the morning and lighter in the evening; Yin Excess pathogens strengthen when encountering Yin, so cold is worse at night and lighter in the day; these are signs of Pathogenic Excess. When Yang is deficient and Yin pathogen attacks the Yang division, illness manifests when Qi circulates through the 25 degrees of Yang, so it is cold during the day and rests at night; when Yin is deficient and Yang pathogen sinks into the Yin division (i.e., Blood division), illness manifests when Qi circulates through the 25 degrees of Yin, so it is hot at night and cool in the day. (Observing malaria occurring either by day or by night confirms this.) These are signs of Righteous Qi deficiency complicated by Pathogens. Cases where heat is severe both day and night indicate Heavy Yang without Yin; cases where cold is severe both day and night indicate Heavy Yin without Yang; cold by day and heat by night indicate intermingling of Yin and Yang. In cases of chronic weakness where symptoms occur irregularly regardless of day or night, it is because Righteous Qi cannot maintain control, and Yin and Yang attack each other with unpredictable victory and defeat. (If a robust person initially presents this, it is due to the struggle between Pathogen and Righteous Qi, causing intermittent disturbance. Observing the alternating chills and fever of Shaoyang syndrome in Shanghan [Cold Damage] shows no fixed schedule, confirming this.)