烦热者。因热而烦。与发热异。发热者但身热而不烦。此则为热所烦。故谓之烦热。经
云。
病患烦热。汗出则解。此证得之于阳热者居多。欲作汗而未能遽汗。往往先有此候。故经又
云
。欲自解者。必当先烦。乃有汗而解。何以知之。脉浮故知汗出解也。浮为在表。在表者宜
汗。故汗出则解也。
凡风寒之邪。由太阳而入者。不即发烦也。至烦而热。为汗解之佳兆。发其汗则热解而
烦亦除
矣。故经云。太阳病。脉浮紧。无汗发热。身疼痛。八九日不解。表证仍在。此当发其汗。
服药已微除。其人发烦热。目瞑。剧者必衄。衄乃解。所以然者。阳气重故也。又云。伤寒
发汗已半日许。复烦。脉浮数者。可更发汗。宜桂枝汤。此皆邪之在太阳者也。太阳病。当
汗不汗。或误与以冷水。或误下者。仲景又施种种救逆诸法。如经云。伤寒若下之。而烦热
胸中窒者。栀子豉汤主之。又云。病在阳应以汗解之。反以冷水 之若灌之。其热被却不
得
去。弥更益烦。肉上粟起。意欲饮水。反不渴者。服文蛤散。若不瘥。与五苓散。盖一因误下
而
阳气陷入胸中。则必解去其胸中之邪。一因误与冷水。而其邪由太阳之经。转入太阳之府。故
不从经解而从府解也。更有太阳证未罢。已转属阳明者。如经云。伤寒表里俱热。舌上干
燥
而烦。白虎加人参汤主之。此由表里俱热。则必以甘寒彻热。使表里俱和。自然得汗而解。又
法之变也。
凡称烦热者。因热而烦。烦在外者也。若烦在内者。另立虚烦一门详后。
烦热，是指因体内有热而感到烦躁。这与单纯的发热不同。发热仅仅是身体发热而没有烦躁感。这里是因为热邪导致烦躁，所以称为“烦热”。
《伤寒论》经文说：“病人出现烦热，出汗后就会痊愈。”这种证候大多是由于阳热之邪引起的。想要通过出汗来解除病邪但暂时还未能出汗时，往往先出现这种症状。因此经文又说：“疾病想要自行解除时，必定会先出现烦躁，随后才会出汗而解。怎么知道呢？因为脉象浮，所以知道会通过出汗而解。脉浮表示病邪在表，病邪在表的应当用发汗法治疗，所以出汗后就会痊愈。”
凡是风寒邪气从太阳经侵入的，不会立即引发烦躁。等到出现烦躁并伴有发热时，这是即将通过出汗而痊愈的好兆头。此时给予发汗治疗，热退而烦躁也会消除。
因此经文说：“太阳病，脉象浮紧，无汗且发热，身体疼痛，经过八九天仍未解除，表证依然存在，这应当使用发汗法。”服药之后症状轻微缓解，但病人出现烦躁、发热、眼睛闭合不想睁开（目瞑），严重的必然会出现鼻出血（衄血），鼻出血后病邪才能解除。之所以这样，是因为阳气郁闭太重的缘故。
经文又说：“伤寒经过发汗治疗后，过了大约半天左右，再次出现烦躁，脉象浮数，可以再次发汗，适宜使用桂枝汤。”这些情况都是邪气仍在太阳经的表现。对于太阳病，应当发汗却没有发汗，或者误用冷水喷洒浇淋，或者误用泻下法，张仲景又施用了各种救逆的方法。
如经文所说：“伤寒如果误用泻下法，导致烦热且胸中窒塞的，用栀子豉汤主治。”
经文又说：“病在阳分（表证）应当用汗法解表，反而用冷水喷洒或浇淋，热气被冷水遏制无法散发，更加烦躁，皮肤上起鸡皮疙瘩，想喝水却并不觉得口渴的，服用文蛤散。如果不好转，给予五苓散。”这是因为一种情况是误用泻下导致阳气陷入胸中，必须解除胸中的邪气；另一种情况是误用冷水，邪气由太阳经传入太阳腑，所以不从经络解表而从腑脏化解。
更有太阳证尚未罢除，已经转属阳明经的情况。如经文所说：“伤寒表里俱热，舌上干燥且烦躁的，用白虎加人参汤主治。”这是由于表里俱热，必须用甘寒之法清除热邪，使表里调和，自然出汗而解。这也是治法的变化。
Fanre (Fever with Irritability) refers to irritability caused by internal heat. This differs from simple Fever (Shufa, 发热). Simple fever manifests only as bodily heat without irritability. Here, the heat pathogen causes irritability, hence it is termed "Fanre" (Fever with Irritability).
The Classic states: "When a patient presents with Fanre (Fever with Irritability), sweating will lead to resolution." This syndrome mostly arises from Yang-Heat pathogens. When the body attempts to sweat out the pathogen but cannot do so immediately, this symptom often appears first. Therefore, the Classic further states: "When a disease is about to resolve spontaneously, there must first be irritability, followed by sweating and resolution. How do we know this? Because the pulse is Floating (Fu, 浮), we know that sweating will lead to resolution. Floating indicates the pathogen is in the Exterior (Biao, 表). For pathogens in the Exterior, diaphoresis (sweating method) is appropriate; thus, sweating leads to resolution."
Generally, when Wind-Cold pathogens enter via the Taiyang (Greater Yang) channel, they do not immediately cause irritability. The subsequent appearance of irritability accompanied by heat is a favorable sign indicating impending resolution through sweating. Administering diaphoresis at this stage resolves the heat and eliminates the irritability.
Thus, the Classic states: "In Taiyang Disease, if the pulse is Floating and Tight, with no sweating, fever, and body pain persisting for eight or nine days without resolution, and the Exterior pattern remains, diaphoresis should be administered." After taking the medicine, symptoms may slightly alleviate, but the patient may develop irritability, fever, and a desire to close their eyes (Muming, 目瞑). In severe cases, epistaxis (Nü, 衄) will occur, after which the pathogen resolves. This occurs because the Yang Qi is heavily constrained.
The Classic also states: "After treating Cold Damage with diaphoresis, if irritability recurs after about half a day and the pulse is Floating and Rapid, diaphoresis may be administered again, preferably using Guizhi Tang (Cinnamon Twig Decoction)." These scenarios all indicate that the pathogen remains in the Taiyang channel. In Taiyang Disease, if diaphoresis is indicated but not performed, or if cold water is mistakenly sprayed or poured on the patient, or if purgatives are mistakenly used, Zhang Zhongjing employs various methods to correct these errors.
As the Classic states: "If Cold Damage is treated with purgation, resulting in Fanre (Fever with Irritability) and chest oppression, Zhizi Chi Tang (Gardenia and Fermented Soybean Decoction) should be used."
The Classic further states: "When the disease is in the Yang level (Exterior), it should be resolved by sweating. If instead cold water is sprayed or poured on the patient, the heat is suppressed by the cold and cannot dissipate, leading to increased irritability, gooseflesh on the skin, a desire to drink water but without actual thirst, Wenli San (Clam Shell Powder) should be taken. If there is no improvement, Wuling San (Five-Ingredient Powder with Poria) should be administered." This is because one scenario involves purgation causing Yang Qi to sink into the chest, requiring the elimination of pathogens in the chest; the other involves the use of cold water, causing the pathogen to transfer from the Taiyang Channel to the Taiyang Fu (Bladder/Organ), thus resolving from the Fu organ rather than the Channel.
Furthermore, there are cases where the Taiyang pattern has not yet ceased but has already transferred to the Yangming (Yang Brightness) channel. As the Classic states: "In Cold Damage, if both the Interior and Exterior present with heat, dryness on the tongue, and irritability, Baihu Jia Renshen Tang (White Tiger Decoction plus Ginseng) should be used." This is due to heat in both the Interior and Exterior, necessitating the use of Sweet-Cold herbs to clear heat and harmonize the Interior and Exterior, leading to natural sweating and resolution. This represents a variation in treatment methods.
Whenever "Fanre" (Fever with Irritability) is mentioned, it refers to irritability caused by external heat. If the irritability originates internally, it is categorized separately under "Deficiency Irritability" (Xufan, 虚烦) and discussed in detail later.