《内经》论疟多以风寒暑湿为言。然风与暑，阳邪也。寒与湿，阴邪也。得病之由，多
因夏
伤于暑，汗大泄，腠理开发，因遇夏气 怆之水，寒邪先伏于皮肤，及遇秋令，而新凉束之
，则表邪不能外越，于是乎阴欲入而阳拒之，阳欲出而阴遏之，阴阳相搏而病作矣。其证大
抵多热多寒，或单寒不热，或单热不寒，或先寒后热，
或先热后寒，或有汗无汗，或汗多汗少，或头疼骨
痛，大渴引饮，或呕吐不思食，或烦
躁不得眠，或大便燥结，或腹满泻利。其浅者，病在三阳，能随卫气以为出入，而一日一作
；其深者，病在三阴，则邪气不能与卫气并出，故或间日一作，或三四日作。作愈迟者，其
病愈深。是以疟之轻重，惟在阴阳浅深，于《本经》则有寒温瘅疟，及六经五脏之分，语无
漏义矣。丹溪复有食水痰饮败血之别，此不过疟之兼证耳，岂果因此而成疟哉？其外如瘴疟
者
，出岭南瘴湿之地。牝疟者，多生阳气不足之人。劳疟者，表里气虚，因劳所发。鬼疟者，
本无疟鬼，邪气乱神。故治疟者，当察其邪之深浅，证之阴阳，必令其自脏而腑，自里而表
，由阴而阳，由晏而蚤，引而散之，升而举之，使邪气得出，自然和矣。至于痰食血气，内
寒内热等证，不过随其甚者而兼治之，弗得以此为主而兼补。然邪在阳者取汗易，邪在阴者
取汗难。又热多者，凉药为灵，寒多者，温药为主。其有外受风寒，内伤生冷，表里俱虚，
则疟痢并作者，以疟感由经，痢感由藏，但兼表里而去，其温湿之本，亦必渐愈也。
《黄帝内经》中论述疟疾，多从风、寒、暑、湿四个方面进行阐述。然而，风和暑属于阳邪，寒和湿属于阴邪。发病的原因，大多是因为夏季感受了暑邪，导致大汗淋漓，腠理（皮肤毛孔）开泄，此时又遇到冷水刺激，寒邪便潜伏在皮肤之中；等到秋季来临，新的凉气束缚体表，使得表邪不能向外发散，于是出现阴气想要进入体内而阳气拒绝它，阳气想要外出而阴气遏制它的局面，阴阳二气相互搏结，疾病因此发作。
其症状大体上多见寒热往来，或者只有寒冷没有发热，或者只有发热没有寒冷，或者先感到寒冷随后发热，或者先感到发热随后寒冷；有的有汗，有的无汗，或者汗多汗少；有的头痛骨痛，极度口渴想喝水，或者呕吐不想进食，或者烦躁无法入睡，或者大便干结，或者腹部胀满伴有腹泻痢疾。病情较浅的，病位在三阳经，能够随着卫气的运行而出入，所以每天发作一次；病情较深的，病位在三阴经，邪气不能与卫气同时外出，所以或者隔日发作一次，或者三四天发作一次。发作时间越晚，说明病情越深。因此，疟疾的轻重，关键在于阴阳的浅深程度。在《神农本草经》中则有寒疟、温疟、瘅疟之分，以及六经、五脏的分类，论述详尽没有遗漏义理。
朱丹溪又提出了因饮食停滞、水饮、痰饮、败血等不同情况的区别，这不过是疟疾的兼夹证候罢了，难道真的是因为这些因素才形成疟疾吗？此外，如瘴疟，产生于岭南地区瘴气湿气重的地方；牝疟（阴性疟疾），多见于阳气不足的人；劳疟，是由于表里气虚，因劳累而诱发；鬼疟，本无所谓的“疟鬼”，而是邪气扰乱心神所致。
因此，治疗疟疾，应当观察邪气的深浅，辨别证候的阴阳属性，务必使病邪从脏传至腑，从里传至表，由阴转阳，由发作时间晚（晏）转为早（蚤），引导并疏散邪气，提升并举升正气，使邪气得以排出，身体自然调和。至于痰食、血气阻滞、内寒、内热等证候，不过是根据其中严重的情况兼以治疗，不能以此为主而单纯进补。然而，邪气在阳经者，发汗容易；邪气在阴经者，发汗困难。另外，热象多的，用凉药有效；寒象多的，以温药为主。如果有外感风寒、内伤生冷，导致表里俱虚，从而疟疾与痢疾同时发作的，因为疟疾的病邪由经络传入，痢疾的病邪由脏腑受累，只要兼顾表里进行治疗，其温湿的根本原因，也必然会逐渐痊愈。
The *Huangdi Neijing* (Yellow Emperor's Inner Canon) discusses malaria (*Nue*, Malaria), often attributing it to wind, cold, summer-heat, and dampness. However, wind and summer-heat are yang pathogens, while cold and dampness are yin pathogens. The cause of illness is mostly due to summer-heat injury in summer, where excessive sweating causes the couli (pores) to open. If one encounters cold water during this time, cold pathogens first lie latent in the skin. When autumn arrives, the new coolness binds the exterior, preventing the exterior pathogens from dispersing outward. Consequently, yin desires to enter but yang rejects it; yang desires to exit but yin obstructs it. The struggle between yin and yang leads to the onset of disease.
The symptoms generally manifest as alternating chills and fever, or only chills without fever, or only fever without chills, or chills preceding fever, or fever preceding chills. There may be sweating or no sweating, or varying degrees of sweat. Other symptoms include headache and bone pain, extreme thirst with a desire to drink, vomiting and loss of appetite, irritability and insomnia, dry and constipated stools, or abdominal fullness with diarrhea and dysentery. When the pathology is shallow, it resides in the Three Yang meridians and moves in and out with the Wei Qi (Defensive Qi), resulting in daily attacks. When the pathology is deep, it resides in the Three Yin meridians, and the pathogenic factor cannot exit together with the Wei Qi, resulting in attacks every other day or every three to four days. The later the attack occurs, the deeper the pathology. Therefore, the severity of malaria depends on the depth and superficiality of yin and yang. In the *Shennong Bencao Jing* (Divine Farmer's Materia Medica), there are distinctions among cold malaria, warm malaria, and dan malaria, as well as classifications according to the Six Meridians and Five Zang Organs, providing comprehensive and exhaustive explanations.
Zhu Danxi further distinguished cases based on food stagnation, fluid retention, phlegm-fluid, and blood stasis. These are merely concurrent syndromes of malaria, not the primary causes of malaria itself. Additionally, zhang malaria arises from the miasma and dampness of the Lingnan region. Pin malaria (yin-type malaria) commonly occurs in individuals with insufficient yang qi. Lao malaria (labor-induced malaria) results from deficiency of qi in both the interior and exterior, triggered by overexertion. Gui malaria (ghost malaria) involves no actual "ghost," but rather pathogenic factors disturbing the spirit (Shen).
Therefore, when treating malaria, one must examine the depth of the pathogen and differentiate the yin-yang nature of the syndrome. The treatment should aim to guide the pathogen from the Zang organs to the Fu organs, from the interior to the exterior, from yin to yang, and shift the timing of attacks from late (yan) to early (zao). By guiding and dispersing the pathogen, and lifting and raising the healthy qi, the pathogen can be expelled, leading to natural harmony. Regarding syndromes such as phlegm-food retention, blood-qii obstruction, internal cold, and internal heat, these should be treated concurrently based on their severity, but they should not be the primary focus for tonification. However, when the pathogen is in the Yang meridians, inducing sweating is easy; when the pathogen is in the Yin meridians, inducing sweating is difficult. Furthermore, if heat predominates, cooling herbs are effective; if cold predominates, warming herbs are primary. In cases where external wind-cold and internal damage from raw/cold foods lead to deficiency in both the exterior and interior, causing simultaneous malaria and dysentery, since the malaria pathogen enters via the meridians and the dysentery pathogen affects the zang organs, treating both the exterior and interior simultaneously will gradually resolve the root cause of damp-warmth, leading to recovery.