伤寒阴阳易之为病。其人身体重。少气。少腹里急。或引阴中拘挛。热上冲胸。头重不欲举。眼中生花。膝
胫拘急者。烧 散主之。
旧注云。大病新瘥。气血未复。余热未尽。强合阴阳而得病者。名曰易。男子病新瘥。
未平复而妇人与之交。妇人得病。名曰阳易。妇人病新瘥。未平复而男子与之交。男子得病。名曰阴易。以愚
意推之。盖以二气 。其构精之时。乃化醇之候也。二气不杂。两精融一。故能化生。所谓二五之精。妙合而凝也。
然男病易之于女。女病易之于男。其受病之人。并非气血未复者。实为注家之误。但男女一交之后。自然元气空虚。
余邪错杂于精气之中。走入精隧。溢入经络。乘其交后虚隙之中。入而浸淫于脏腑筋骨。脉络 穴之间。则正气
因邪而益虚。邪气因虚而益盛。故有此阴盛阳
衰之诸证也。邪入阴经。身体必重。真阳亏损。三焦不运。宗气不行。所以少气。邪从阴窍而溜入少阴厥阴。
故少腹里急。若里急之甚。或引阴中拘挛。皆阴邪之所致也。阴邪在下而虚阳上走。故热上冲胸。头重不欲举。
眼中生花。下焦虚冷。所以膝胫拘急也。此真所谓阴阳之患。故以烧 散主之。
烧 散方
上取妇人中 近隐处。剪烧灰。以水和服方寸匕。日三服。小便即利。阴头微肿则愈。妇人病。取男子
裆烧灰。
或谓阴阳易之证。近于变幻。故用烧 之法。亦近于厌禳。曰非也。有至理存焉。男女之交媾。易所谓二
气感应以相与也。以未净之邪。随交合之情。精神魂魄。无不动摇。翕然而感。感而遂通。混入于少阴之里。
故以近隐处之 裆。引出其阴中之邪。所谓物从其类。同气相求之义也。但此方当为导引之药。其余当随其脉症
之阴阳寒热。治之可也。如王海藏之脉在厥阴。当以当归四逆汤。下烧 散。在少阴。当以通脉四逆汤下烧 散。
在太阴。当以理中丸同下烧 散。所用之药。各随其经而效自速也。不然。则有阴肿或缩。少腹绞痛。手足蜷。
脉绝而死者。其后人之青竹茹汤。及 鼠粪汤。恐未必能合原文中之诸阴症也。大凡易病。必有如前诸证者方是。
如无此见证。不过传染之证耳。
The disease known as "Yin-Yang Exchange" (Yin Yang Yi, a condition transmitted between partners after recovery from severe febrile disease) in post-shanghan syndrome. The patient experiences heaviness of the body, shortness of breath (Shao Qi), urgency and tightness in the lower abdomen, or spasms drawing into the genitalia, heat rushing up to the chest, heaviness of the head making it difficult to lift, blurred vision or seeing spots before the eyes, and stiffness/spasms of the knees and shins. This condition should be primarily treated with Shao Kun San (Burnt Underwear Powder).
Old annotations state: After a major illness has just healed, if sexual intercourse is forced while the vital qi and blood have not yet recovered and residual pathogenic heat remains, resulting in illness, it is named "Exchange". If a man, newly recovered from illness and not yet fully restored, engages in intercourse with a woman, and she contracts the disease, it is called "Yang Exchange" (Yang Yi). If a woman, newly recovered from illness and not yet fully restored, engages in intercourse with a man, and he contracts the disease, it is called "Yin Exchange" (Yin Yi). In my opinion, this reasoning is flawed. The essence of conception lies in the harmonious blending of two qi during intercourse. However, the person contracting the disease through exchange is not suffering because their qi and blood were un-recovered; rather, they are healthy but become infected. The error lies in the old annotations. It is only that after sexual intercourse, the primordial qi naturally becomes deficient. Residual pathogens mix within the essence and qi, entering the spermatic channels, overflowing into the meridians, and taking advantage of the void left by intercourse to infiltrate the zang-fu organs, sinews, bones, and acupoints. Consequently, righteous qi becomes more deficient due to the pathogen, and the pathogen becomes more vigorous due to deficiency, leading to these symptoms of yin excess and yang decline. Pathogens entering the yin meridians cause body heaviness; loss of true yang and failure of the San Jiao (Triple Burner) to transport, along with stagnation of Zong Qi (Gathering Qi), result in shortness of breath. Pathogens slipping from the yin orifices into the Shaoyin (Lesser Yin) and Jueyin (Terminal Yin) meridians cause lower abdominal urgency. Severe urgency may draw into genital spasms, all caused by yin pathogens. With yin pathogens below and deficient yang floating upward, heat rushes to the chest, the head feels heavy and hard to lift, and vision blurs. Cold in the lower jiao causes stiffness of the knees and shins. This is truly a disorder of yin and yang, hence treated with Shao Kun San.
Formula: Shao Kun San (Burnt Underwear Powder)
Take the part of the woman's undergarment closest to the genitals, cut it off, burn it to ash, mix with water, and administer one cun-bi (a measure roughly equivalent to a tablespoon) per dose. Take three times daily. When urination becomes smooth and the glans penis swells slightly, the patient will recover. For women suffering from this, take the man's undergarment裆 (crotch area), burn it to ash, and administer similarly.
Some argue that the symptoms of Yin-Yang Exchange are变幻 (capricious/changing), so using burnt underwear seems akin to witchcraft or apotropaic magic. I say this is incorrect; there is profound logic herein. Sexual intercourse is the mutual interaction of two qi, as stated in the I Ching. Unpurified pathogens, driven by sexual desire, shake the spirit and soul, inducing rapid resonance and penetration into the interior of the Shaoyin meridian. Thus, using the underwear from the genital region draws out the pathogens hidden in the yin, following the principle of "things follow their kind, and similar qi seeks each other." However, this formula should serve only as a guiding agent. Subsequent treatment must be based on the yin-yang and cold-heat nature of the pulse and symptoms. For instance, Wang Haizang suggested: if the pulse indicates involvement of the Jueyin meridian, administer Shao Kun San with Danggui Sini Tang (Cinnamon Twig and Angelica Decoction); if involving Shaoyin, use Tongmai Sini Tang (Pulse-Reviving Decoction); if involving Taiyin, use Lizhong Wan (Regulate the Middle Pill). Medications should correspond to the affected meridian for rapid efficacy. Otherwise, complications such as scrotal swelling or retraction, severe lower abdominal colic, curling of hands and feet, and absent pulse leading to death may occur. Later formulas like Qingzhuru Tang (Green Bamboo Shoot Decoction) and Shufen Sui Tang (Rat Feces Decoction) likely do not align with the yin-syndromes described in the original text. Generally, for Yin-Yang Exchange to be diagnosed, the aforementioned symptoms must be present. Without these specific manifestations, it is merely an infectious disease.