郭稽中曰∶产后乍寒乍热者何？答曰∶阴阳不和，败血不散，能令乍寒乍热也。产后血气虚损，阴阳不和，
阴胜则乍寒，阳胜则乍热，阴阳相乘，则或寒或热。产因劳伤脏腑，血弱不得宣越，故令败血不散。入于肺
则热，入干脾则寒。医人误作疟治，则谬矣。阴阳不和，宜增损四物汤。败血不散，宜夺命丹。又问二者何以
别之？曰∶时有刺痛者，败血也。但寒热无他证者，阴阳不和也。
陈无择曰∶产后乍寒乍热，荣卫不和，难以轻议。若败血不散，岂止脾肺二脏。大抵一阴闭一阳，即作寒
热。阴胜故寒，阳胜故热。只可云败血循经流入，闭诸阴则寒，闭诸阳则热，血气与卫气解则休，遇再会而复
作，大调经散，入醋煎佳。
武叔卿曰∶闭阴闭阳之说，率难理解。败血闭阴则寒，闭阳则热，而有休解会作之时，则似疟矣。若瘀血，
为有形之物，闭则壅矣，安有解会之所。愚谓血闭于阳经，荣卫行之不通则寒；血闭于阴经，荣卫行之不通则
热，故必瘀通而寒热自已。又，就大调经散而言，行瘀于内也；五积散，行瘀于外也。又，外经或为寒客则肺
病，肺病而荣卫不通则热；内腑或为冷物所伤则脾病，脾病而荣卫不通则寒。故所用之方，一主里，一主表，
亦或内外俱瘀，则寒热并作，二药又均不可废。
Guo Jizhong said: What is the cause of alternating chills and fever (Zha Han Zha Re) after childbirth? The answer is: Disharmony of Yin and Yang, and retention of lochia (postpartum residual blood), can cause alternating chills and fever. After childbirth, Qi and Blood are deficient and damaged, leading to disharmony of Yin and Yang. When Yin prevails, there are sudden chills; when Yang prevails, there are sudden fevers. As Yin and Yang interfere with each other, symptoms may alternate between cold and heat. Childbirth involves fatigue that damages the Zang-Fu organs, causing Blood deficiency and failure to circulate freely, thus resulting in retained lochia. If lochia enters the Lung, it causes fever; if it invades the Spleen, it causes chills. If physicians mistakenly treat this as malaria (Nue Ji), they would be erroneous. For disharmony of Yin and Yang, Zengsun Siwu Tang (Modified Four Substance Decoction) is appropriate. For retained lochia, Duoming Dan (Life-Restoring Pill) is appropriate. Asked how to distinguish these two conditions: If there are stabbing pains at times, it is retained lochia. If there are only alternating chills and fever without other symptoms, it is disharmony of Yin and Yang.
Chen Wuyue said: Alternating chills and fever after childbirth indicates disharmony of Ying and Wei (Nutritive and Defensive Qi), making it difficult to make hasty judgments. If lochia is retained, does it not affect more than just the Spleen and Lung? Generally, when one Yin and one Yang channel are obstructed, chills and fever occur. Preponderance of Yin causes chills; preponderance of Yang causes fever. It can be stated that retained lochia flows along the meridians; obstruction of the various Yin channels leads to chills, while obstruction of the various Yang channels leads to heat. Symptoms cease when Blood and Qi harmonize with Wei Qi, but recur upon their next convergence. Da Tiaojing San (Great Regulation of Menstruation Powder) is recommended, preferably decocted with vinegar.
Wu Shuqing said: The theory of "obstructing Yin" and "obstructing Yang" is generally difficult to comprehend. Retained lochia obstructing Yin channels causes chills, and obstructing Yang channels causes fever. The presence of periods of remission and recurrence resembles malaria. However, stasis blood is a tangible substance; once obstructed, it becomes congested. How can there be a state of resolution and re-convergence? I propose that when blood is obstructed in Yang channels, the unimpeded flow of Ying and Wei leads to chills; when blood is obstructed in Yin channels, the unimpeded flow of Ying and Wei leads to heat. Therefore, only by resolving the stasis will the chills and fever subside naturally. Furthermore, regarding Da Tiaojing San, it resolves stasis internally; Wuji San (Five Accumulations Powder) resolves stasis externally. Additionally, external channels invaded by cold pathogens lead to Lung pathology, where impaired Ying and Wei circulation causes fever; internal organs injured by cold substances lead to Spleen pathology, where impaired Ying and Wei circulation causes chills. Thus, the prescribed formulas target interior and exterior conditions respectively. If both interior and exterior involve stasis, causing simultaneous chills and fever, neither medicine should be discarded.