凡伤寒初感之治，本与传变者不同。盖凡病伤寒、瘟疫者，无不发热，然初感之时，其
邪在表，未经传里，未至郁热，虽身表有热，不过肤腠之寒邪，而内未有火，岂即阳证。斯
时也，但用温散，或兼托散，药对其证，无不即愈。奈何时俗之医，一见发热，便认为火，
而芩、连、知、柏，开手便用，不知内无实热，何以当此？以寒邪得寒药，而表里俱寒，勾
连不解，则日以内传，寒凉妄用，则元阳日败。凡受斯害，死者多矣。此理不明，则既不知
表里，又不知先后，终身不省，每致误人，而且敢侈口谈医，其心果亦安乎？
凡伤寒饮食有宜忌者，有不宜忌者。若病伤寒而食不断者，以邪犹在表，未深入也。及
其稍深，而在半表半里之间，则食渐减矣，再入胸膈、胃口，则全不食矣。邪既在胃，则胃
口不饥，所以伤寒不食者，或十日，或二十日，皆无足虑者，亦以胃气不馁，则不败也。第
不欲食者，不可强食，强食则助邪；或新愈之后，胃气初醒，尤不可纵食，纵食则食复，此
皆大忌也。至有不宜忌者，则如劳倦内伤之人，偶感寒邪，亦必发热，此多以劳伤中气，
本非真正伤寒外邪内陷之病，所以外虽发热，而内则饥馁，每多思食。奈何庸昧之辈，但见
发热，则曰饿不死伤寒，不论虚实，一概禁之。常见欲食者，索之不得，而且加以克伐寒凉
之药，嗟嗟！饥肠受剥，虚者益虚，内外夹攻，苦无所诉，及胃气既脱，反不欲食矣。即欲
救之，已无可及。余常治此证，每借食为药，所活多人，而见禁食受毙者，亦已不少，故详
言之。若病患时时觉饥而索食者，此其邪不在脏，胃中空虚而然，必不可禁，但不宜纵耳。
且因此可察虚实，关系非小，不可忽也。
巢氏曰∶凡瘟疫病新瘥，脾胃尚虚，谷气未复。若作劳妄动伤力，并食猪羊、鸡犬、鱼
脍、灸爆、肥腻、生果、面食、硬涩难消之物，停积肠胃，膈闷腹胀，便秘，或大吐大
下。重复发热，病作不可救矣。
凡伤寒初感的治疗，本来与病邪传变后的治疗是不同的。大概凡是患伤寒、瘟疫的人，没有不发热的，然而在初感之时，病邪在体表，尚未传入里部，未达到郁结化热的程度，虽然身体表面有热，不过是肤表腠理间的寒邪，而体内并没有火邪，怎么能立即判定为阳证呢？这个时候，只要使用温性发散的药物，或者兼用托散之法，药证相符，没有不立刻痊愈的。无奈当时的世俗医生，一见发热，便认为是火邪，起手就用黄芩、黄连、知母、黄柏等寒凉药物，不知道体内没有实热，怎么能承受这些药物？以寒邪遇到寒药，导致表里俱寒，勾连纠缠不解，那么病邪就会一天天向内部传变；妄用寒凉药物，就会使元阳一天天败坏。凡是遭受这种危害的人，死去的很多。这个道理如果不明白，就既不知道表里的区别，又不知道治疗的先后顺序，终身都不醒悟，常常导致误人，而且还敢夸夸其谈谈论医术，他们的良心真的安吗？
凡是伤寒饮食方面有适宜和禁忌的，也有不适宜禁忌的。如果患伤寒但食欲不断绝的，是因为邪气还在体表，没有深入。等到邪气稍深，处于半表半里之间时，食欲就会逐渐减少；再进入胸膈、胃口部位时，就完全不想吃东西了。邪气既然在胃，胃口就不觉得饥饿，所以伤寒期间不吃饭，无论是十天还是二十天，都无需担忧，也是因为胃气没有衰竭，就不会败坏。只是不想吃东西的时候，不可以强迫进食，强迫进食则会助长邪气；或者刚痊愈之后，胃气刚刚苏醒，尤其不可以放纵饮食，放纵饮食则会导致“食复”（因饮食不当导致的复发），这些都是大忌。至于有不适宜禁忌的情况，比如劳倦内伤的人，偶尔感受寒邪，也必然发热，这大多是因为劳损伤了中气，本不是真正的伤寒外邪内陷的病，所以外表虽然发热，内部却感到饥饿，往往很想吃东西。无奈那些庸俗无知之辈，只见到发热，就说“饿不死伤寒”，不论虚实，一概禁止进食。常见想吃东西的人，求之不得，反而加上攻伐寒凉的药物，唉！饥饿的肠胃受到剥蚀，虚弱者更加虚弱，内外夹攻，痛苦无处诉说，等到胃气脱绝，反而不想吃东西了。即使想要救治，也已经来不及了。我常治疗这类病症，每每借助食物作为药物，救活了很多人的，而见到因被禁止进食而死亡的，也已经不少，所以详细说明这些道理。如果病人时时觉得饥饿并索要食物的，这是邪气不在脏腑，而是胃中空虚所致，绝对不可以禁止，只是不宜放纵罢了。并且由此可以察知虚实，关系重大，不可忽视。
巢元方说：凡是瘟疫病刚痊愈，脾胃尚且虚弱，谷气尚未恢复。如果劳作妄动损伤体力，以及食用猪羊、鸡犬、鱼生、烧烤、肥腻、生冷水果、面食、坚硬涩滞难消化的食物，停滞积聚在肠胃，导致胸膈闷胀、腹胀、便秘，或者大吐大泻。再次发热，病作不可救矣。
The treatment of initial contraction in Shanghan (Cold Damage) is inherently different from that of transmitted diseases. Generally, all patients suffering from Shanghan or plague exhibit fever. However, at the time of initial contraction, the pathogenic factor remains in the exterior, has not yet transmitted to the interior, and has not reached a state of stagnant heat. Although there is heat on the body surface, it is merely cold pathogenic factors affecting the skin and interstices, with no internal fire; thus, how can it be immediately diagnosed as a Yang syndrome? At this stage, one should simply use warm dispersing herbs, or combine them with supporting dispersing methods. If the prescription matches the syndrome, recovery will occur promptly. Regrettably, contemporary physicians, upon seeing fever, invariably attribute it to fire and immediately prescribe cold-natured herbs such as Huangqin (Scutellariae Radix), Lianzi (Coptidis Rhizoma), Zhimu (Anemarrhenae Rhizoma), and Baipiao (Phellodendri Cortex). They fail to realize that without excess heat in the interior, these herbs are ill-suited. Applying cold herbs to cold pathogens results in coldness in both the exterior and interior, causing the pathogen to linger unresolved and transmit inward day by day. The reckless use of cold-cooling agents leads to the daily decline of Yuan Yang (Primal Yang). Many have died due to such harm. If this principle is not understood, one fails to distinguish between the exterior and interior, neglects the sequence of treatment, remains ignorant throughout life, frequently causes medical errors, and yet dares to speak arrogantly about medicine. How can their conscience be at peace?
Regarding diet in Shanghan, some items are suitable, some are contraindicated, and others need not be restricted. If a patient with Shanghan retains their appetite, it indicates the pathogen remains in the exterior and has not penetrated deeply. As the pathogen moves slightly deeper into the Shaoyang (Half-Exterior, Half-Interior) region, appetite gradually decreases. Once it enters the chest, diaphragm, and stomach area, appetite ceases completely. When the pathogen resides in the Stomach, the desire for food diminishes. Therefore, lack of appetite during Shanghan, whether lasting ten or twenty days, is not a cause for concern, provided the Stomach Qi remains robust and does not collapse. However, when appetite is absent, forcing food intake should be avoided, as it may exacerbate the pathogen. Similarly, after recent recovery, when Stomach Qi is just beginning to revive, one must not indulge in eating, as doing so may lead to "Food Relapse" (recurrence of disease due to improper diet); these are major taboos. Conversely, there are cases where dietary restriction is inappropriate. For instance, individuals suffering from fatigue-induced internal injury who contract cold pathogens will also develop fever. This is primarily due to damage to Middle Jiao Qi from overexertion, rather than true external cold invading the interior. Thus, although there is external fever, the interior feels empty and hungry, often creating a strong desire to eat. Unfortunately, mediocre and ignorant physicians, seeing only fever, claim that "starvation cannot kill Shanghan," and indiscriminately prohibit food regardless of deficiency or excess. It is common to see patients desiring food but being denied it, while simultaneously receiving attacking and cold-cooling prescriptions. Alas! The hungry intestines are further depleted, the deficient become more deficient, subjected to attacks from both inside and outside, with nowhere to turn for relief. By the time Stomach Qi collapses, they lose even the desire to eat. Even if one wishes to save them, it is too late. I often treat such conditions, using food as medicine, saving many lives, while witnessing numerous deaths caused by forced fasting. Hence, I elaborate on this matter. If a patient constantly feels hunger and seeks food, it indicates the pathogen is not in the Zang-Fu organs but rather due to emptiness in the Stomach; such cases absolutely must not restrict food, though indulgence should be avoided. This observation helps discern deficiency and excess, which is significant and should not be neglected.
Chao Yuanfang stated: After the recent recovery from plague, the Spleen and Stomach remain weak, and Gu Qi (Grain Qi/Nutritive Energy) has not yet recovered. If one engages in laborious exertion or consumes pork, mutton, chicken, dog, raw fish, roasted foods, fatty/greasy items, raw fruits, wheat products, or hard/astringent foods difficult to digest, these will stagnate and accumulate in the intestines and stomach. This leads to chest oppression, abdominal distension, constipation, or severe vomiting and diarrhea. Fever may recur, and the condition may become incurable.