感六淫而即发病者，轻者谓之伤，重者谓之中；感六淫而不即病，过后方发者，总谓之曰伏邪。已发者而治不得法，
病情隐伏，亦谓之曰伏邪。有初感治不得法，正气内伤，邪气内陷，临时假愈，后乃复作者，亦谓之曰伏邪；有已发治
愈，而未能除尽病根，遗邪内伏，后又复发，亦谓之曰伏邪。夫伏邪，有伏燥，有伏寒，有伏风，有伏湿，有伏暑，有
伏热。
四时之序，春为风，夏为暑，长夏为湿，秋为燥，冬为寒，皆有外因。火则本无外因，然《内经》言百病之生，皆
生于风寒暑湿燥火，则并及于火为六，病则名曰六淫。盖以风暑湿燥寒感于外，火即应之于内；则在内之火，即此在外
之五气有以致之，故火但曰游行其间，后贤所以有五气皆从火化之说也。
凡伏气温热，皆是伏火，虽其初感受之气，有伤寒伤暑之不同，而潜伏既久，蕴酿蒸变，超时而发，无一不同归火
化。中医所谓伏火症，即西医所谓内炎症也。王秉衡曰∶风寒暑湿，悉能化火，血气郁蒸，无不生火，所以人之火症独
多焉。朱心农曰∶东南方天时多热，地气多湿，最多湿热湿温之症，正伤寒症极少。即云冬月多正伤寒症，亦不尽然。
历症以来，恒见大江以南，每逢冬令太温，一遇感冒，表分虽有外寒，内则竟多伏火，悉以伏火治之，丝毫不爽。故魏
柳州曰∶壮火为万病之贼。嘉约翰曰∶炎症为百病之源。中医西医，其揆一也。虽然，同一伏火，而湿火与燥火判然不
同。以治燥火之法治湿火，则湿欲遏而热愈伏，势必为痞满，为呕呃，为形寒，热不扬，为肠鸣泄泻，甚则蒙闭清窍，
谵语神昏，自汗肢厥，或口噤不语，或手足拘挛；以治湿火之法治燥火，则以燥济燥，犹拨火使扬，势必为灼热，为消
渴，为热盛昏狂，为风动痉厥，甚则鼻煽音哑，舌卷囊缩，阴竭阳越，内闭外脱。是以对症发药，必据燥火湿火之现症
为凭。分际自清，误治自少。
凡是感受六淫邪气而立即发病的，病情轻的称为“伤”，病情重的称为“中”；感受六淫邪气后不立即发病，过了一段时间后才发作的，总称为“伏邪”。已经发病但治疗不得法，导致病情隐伏在内，也称为“伏邪”。有初次感受邪气时治疗不得法，导致正气内伤、邪气内陷，当时看似暂时好转（假愈），后来又重新发作的，也称为“伏邪”；有已经发病并治愈，但未能彻底清除病根，遗留邪气潜伏在内，后来又复发的，也称为“伏邪”。所谓伏邪，包括伏燥、伏寒、伏风、伏湿、伏暑、伏热。
四季的顺序是：春季对应风，夏季对应暑，长夏对应湿，秋季对应燥，冬季对应寒，这些都有外在的原因。火则原本没有直接的外在原因，然而《黄帝内经》说各种疾病的发生，都产生于风、寒、暑、湿、燥、火，因此将火也包括在内成为六种致病因素，疾病便称为“六淫”。这是因为风、暑、湿、燥、寒感受于外，火则在体内相应产生；那么体内的火，就是由这五种在外的邪气所导致的，所以火只是游走运行于其间，后世医家因此有了“五气皆从火化”的说法。
凡是伏气温热病，都是伏火，虽然其最初感受的气，有伤寒和伤暑的不同，但潜伏时间既久，蕴酿蒸腾变化，超越时令而发作，最终无一不同归于火化。中医所说的伏火症，即西医所说的内炎症。王秉衡说：风寒暑湿，都能化为火，血气郁结蒸腾，无不生火，所以人的火症特别多。朱心农说：东南方天时多热，地气多湿，最多见的是湿热和湿温病症，真正的伤寒症极少。即使说冬天多有真正的伤寒症，也不尽然。根据历年病例来看，恒常看到长江以南地区，每逢冬季气候过于温暖，一旦遇到感冒，体表虽然有外寒，体内却多有伏火，全部按照伏火来治疗，丝毫不差。所以魏柳州说：壮火（亢盛的火热之邪）是万病的贼寇。嘉约翰说：炎症是百病的根源。中医和西医，道理是一致的。虽然如此，同样是伏火，但湿火与燥火截然不同。如果用治疗燥火的方法来治疗湿火，则湿气被遏制而热邪更加潜伏，势必导致痞满、呕吐呃逆、怕冷、热势不扬、肠鸣泄泻，甚至蒙蔽清窍、谵语神昏、自汗肢冷，或者牙关紧闭不语，或者手足拘挛抽搐；如果用治疗湿火的方法来治疗燥火，则是以燥助燥，如同拨动火使其扬起，势必导致灼热、消渴、热盛昏狂、肝风内动痉厥，甚至鼻翼扇动声音嘶哑、舌卷囊缩、阴液枯竭阳气外越、内闭外脱。因此对症用药，必须依据燥火或湿火的现症作为凭据。分际自然清晰，误治自然减少。
Those who contract the Six Excesses (Liu Yin, 六淫) and fall ill immediately are said to have a "Shang" (Injury, 伤) if the condition is mild, or a "Zhong" (Strike/Severe Injury, 中) if it is severe. Those who contract the Six Excesses but do not fall ill immediately, instead manifesting symptoms after a period of time, are collectively referred to as having "Fu Xie" (Latent Pathogenic Factors, 伏邪). If an already manifested illness is treated improperly, causing the pathology to lie latent within, it is also called "Fu Xie". If the initial contraction was treated improperly, damaging the Zheng Qi (Upright Qi, 正气) internally and allowing the pathogen to sink inward, resulting in a temporary false recovery followed by relapse, this is also called "Fu Xie". If an illness has been treated and cured but the root cause was not completely eradicated, leaving residual pathogens to lie latent and later recur, this is also called "Fu Xie". These latent pathogens include Latent Dryness (Fu Zao, 伏燥), Latent Cold (Fu Han, 伏寒), Latent Wind (Fu Feng, 伏风), Latent Dampness (Fu Shi, 伏湿), Latent Summerheat (Fu Shu, 伏暑), and Latent Heat (Fu Re, 伏热).
The sequence of the four seasons is: Spring corresponds to Wind, Summer to Summerheat, Late Summer to Dampness, Autumn to Dryness, and Winter to Cold; all of these have external causes. Fire, however, originally has no direct external cause. Yet, the *Huangdi Neijing* (Yellow Emperor's Inner Canon) states that the generation of myriad diseases arises from Wind, Cold, Summerheat, Dampness, Dryness, and Fire; thus, Fire is included to make six, and such diseases are named "Six Excesses" (Liu Yin, 六淫). This is because Wind, Summerheat, Dampness, Dryness, and Cold affect the exterior, while Fire responds internally; therefore, the internal Fire is induced by these five external factors. Consequently, Fire merely circulates among them, which is why later physicians proposed the theory that "the Five Qi all transform into Fire" (Wu Qi Jie Cong Huo Hua, 五气皆从火化).
All latent Warmth-Heat illnesses are Latent Fire. Although the initial pathogenic factor contracted may differ between Cold Injury (Shang Han, 伤寒) and Summerheat Injury (Shang Shu, 伤暑), once latent for a long time, they undergo fermentation, steaming, and transformation, emerging beyond their proper season, ultimately all returning to the transformation into Fire. The "Latent Fire Syndrome" described in Traditional Chinese Medicine corresponds to "Internal Inflammation" in Western medicine. Wang Bingheng stated: "Wind, Cold, Summerheat, and Dampness can all transform into Fire; blood and Qi stagnation and steaming invariably generate Fire, which is why Fire syndromes are particularly numerous in humans." Zhu Xinnong stated: "In the Southeast, the heavenly climate is often hot, and the earthly qi is often damp, making Damp-Heat and Damp-Warmth syndromes most common, while true Cold Injury syndromes are rare. Even if one claims that winter sees many true Cold Injury syndromes, this is not entirely accurate. Based on historical cases, it is consistently observed that in regions south of the Yangtze River, whenever the winter is unusually warm, upon contracting a cold, although there is exterior Cold, the interior predominantly contains Latent Fire. Treating all cases according to Latent Fire yields precise results without error. Therefore, Wei Liuzhou stated: 'Zhuang Huo' (Exuberant Fire, 壮火) is the thief of ten thousand diseases." John Chalmers stated: "Inflammation is the source of hundred diseases." The principles of TCM and Western medicine are identical. Nevertheless, although both are Latent Fire, Damp-Fire and Dry-Fire are distinctly different. Using methods for treating Dry-Fire on Damp-Fire will suppress the Dampness while trapping the Heat further, inevitably leading to fullness and obstruction, vomiting and hiccups, aversion to cold, obscured heat sensation, borborygmus, and diarrhea, and potentially clouding the clear orifices, delirium and coma, spontaneous sweating, cold limbs, jaw clenching with inability to speak, or limb spasms and convulsions. Conversely, using methods for treating Damp-Fire on Dry-Fire adds dryness to dryness, akin to fanning flames, inevitably leading to scorching heat, Xiao Ke (Wasting-Thirst, 消渴), extreme heat with confusion and mania, wind stirring leading to spasms and syncope, and potentially flaring nostrils with hoarseness, curled tongue and retracted scrotum, exhaustion of Yin with floating of Yang, internal closure with external collapse. Therefore, prescribing medication based on symptoms must rely on the presenting signs of either Dry-Fire or Damp-Fire. When distinctions are clear, mis-treatment naturally decreases.