【纲】仲景曰。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。
【目】王好古曰。阴阳易病。当诊脉随症治之。若脉在厥阴。当归四逆送下本散。脉在少阴。
通脉四逆汤送下本散。脉在太阴。四顺理中丸煎汤送下本散。所用之药。各随其经而效自速也。
张元素曰。假如妇人病新瘥。未平复。男子与交。因感外邪卒病。实非余邪相染。医见病速。
谓之阴易。于法何以别乎。夫易症者。有本条所见之症存焉。其与外所感。岂相侔哉。设若风寒外
伤。当有表症。安有少腹里急引阴中拘挛者乎。或又云。假如男子病新瘥。强合阴阳而自病。仍小
腹里急引阴中拘挛。症同易病。求其理。何故不染易他人而自复。未审其症治。可同何法也。曰。
病虽有复。理与易同。亦用烧 散以安其气。夫易病之为易。阴阳感动余邪。而其人正气本虚。故
能染着。不然。安得受其邪哉。今病自复。缘正气尚虚。而余邪因动。悉非外感。故与易同。亦与
烧散以安正气。正气安。余邪自退矣。
赵嗣真曰。病伤寒人。热毒藏气血中者。渐从表里解散。惟热毒藏于精髓中者。无由发泄。故
瘥后与不病之体交。男女相传。故名阴阳易。即交易之义也。服此散后。小便得利。阴头微肿。阴毒
仍从阴窍出耳。
王肯堂曰。男病而女与交接相染。名阳易。女病而男与交接相染。名阴易。男相染。则阴肿入腹
绞痛。女相染。则里急腰胯连腹内痛。
柯琴曰。此症无内外因。本非伤寒。而冠以伤寒者。原其因也。无恶寒发热之表症。无胃实自
利之里症。因淫情不禁。阴邪得以投其隙。移祸于不病之人。顿令一身之精气形神。皆受欲火之为
害。是不病于伤寒。而病于阴阳之易也。
【纲】张仲景说：伤寒病后发生的阴阳易这种病症，患者身体沉重，气短乏力，小腹部拘急疼痛，或者牵引外阴部痉挛抽搐，热气上冲至胸部，头部沉重不想抬起，眼前发黑视物模糊，膝盖和小腿拘挛僵硬。这种情况用烧裈散（将患者贴身内裤近阴处剪下烧成灰）为主治方剂。
【目】王好古说：治疗阴阳易病，应当根据脉象和症状进行治疗。如果脉象显示病在厥阴经，用当归四逆汤送服本散；如果脉象显示病在少阴经，用通脉四逆汤送服本散；如果脉象显示病在太阴经，用四顺理中丸煎汤送服本散。所用药物各随其所属经络，疗效自然迅速。
张元素说：假如妇女病刚痊愈，身体尚未完全恢复，男子与其性交，因此感受外邪突然发病，这实际上并非余邪相互传染。医生见病情发生迅速，称之为阴易。从医理上如何辨别呢？所谓易症，具备本条文中所述的症状存在。这与外感邪气引起的疾病，难道是一样的吗？假设是风寒外感，应当有表证，怎么会有小腹部拘急并牵引外阴部痉挛的情况呢？又有人说：假如男子病刚痊愈，强行进行房事而自身生病，仍然出现小腹拘急并牵引外阴部痉挛，症状与易病相同。探究其道理，为什么没有传染给他人而是自己复发？审察其症状和治疗，可以用什么方法呢？回答说：虽然病是自复，但医理与易病相同，也用烧裈散来安定正气。所谓易病之所以称为“易”，是因为阴阳感动导致余邪留存，而患者正气本来虚弱，所以能够染着。否则，怎么能受到邪气侵害呢？现在病是自复，因为正气尚且虚弱，而余邪因动而发作，全都不是外感所致，所以与易病相同，也用烧裈散来安定正气。正气安定，余邪自然消退。
赵嗣真说：患伤寒的人，热毒潜伏在气血中的，逐渐从表里解散；只有热毒潜伏在精髓中的，没有途径发泄。所以在病愈后与未患病之体交合，男女之间互相传染，所以叫作阴阳易，即交易的意思。服用此散后，小便通利，阴头轻微肿胀，阴毒仍从阴窍排出。
王肯堂说：男子患病而女子与之交接被传染，名叫阳易；女子患病而男子与之交接被传染，名叫阴易。男子被传染，则阴囊肿胀，疼痛入腹绞痛；女子被传染，则小腹拘急，腰胯连及腹内疼痛。
柯琴说：此症没有内外病因，原本不是伤寒，冠以“伤寒”之名，是追溯其起因。没有恶寒发热的表证，没有胃实自利的里证，因为淫情不能节制，阴邪得以乘虚而入，将祸害转移给未患病之人，顿时令一身精气形神都遭受欲火的危害。这不是病于伤寒，而是病于阴阳之易。
[General Principle] Zhang Zhongjing stated: Regarding the disease of Yin-Yang Exchange (Yin Yang Yi) occurring after Shanghan (Cold Damage), the patient presents with a heavy body, shortness of breath and lack of vital energy, urgency and cramping in the lower abdomen, or pain radiating to the genital area with spasms, heat rushing up to the chest, heaviness of the head making it difficult to lift, visual disturbances such as seeing spots before the eyes, and stiffness and cramping of the knees and calves. This condition is primarily treated with Shao Kun San (Burnt Underwear Powder).
[Detailed Discussion] Wang Haogu stated: In treating the disease of Yin-Yang Exchange, one should diagnose based on the pulse and treat according to symptoms. If the pulse indicates involvement of the Jueyin Meridian (Jueyin Jing), Ben San (the aforementioned powder) should be taken with Danggui Sini Tang (Angelica Decoction for Cold in the Extremities). If the pulse indicates involvement of the Shaoyin Meridian (Shaoyin Jing), Tongmai Sini Tang (Pulse-Reviving Decoction) should be used to take Ben San. If the pulse indicates involvement of the Taiyin Meridian (Taiyin Jing), Sixun Lizhong Wan (Four-Harmony Regulating the Middle Pill) decocted in water should be used to take Ben San. The medications used act quickly when they correspond to their respective meridians.
Zhang Yuansu stated: Suppose a woman has just recovered from an illness but her constitution has not yet fully stabilized, and a man engages in sexual intercourse with her, thereby contracting external pathogens and falling ill suddenly. This is actually not a transmission of residual pathogenic factors between individuals. Physicians, observing the rapid onset of the disease, call it Yin Yi (Yin Exchange). How can this be distinguished medically? The so-called Exchange syndrome possesses the symptoms described in the original text. Is it comparable to diseases caused by external pathogens? If it were an external contraction of Wind-Cold, there should be exterior symptoms. How could there be urgency and cramping in the lower abdomen radiating to the genital area? Others say: Suppose a man has just recovered from an illness but forces sexual intercourse and falls ill himself, still presenting with lower abdominal urgency and cramping radiating to the genital area, with symptoms identical to the Exchange disease. Investigating the rationale, why does he not infect others but rather suffer a recurrence himself? Examining the symptoms and treatment, what method applies? The answer is: Although the disease recurs within the individual, the principle is the same as in the Exchange disease. One also uses Shao Kun San to stabilize the Zheng Qi (Upright Qi/Vital Energy). The reason the Exchange disease is called "Exchange" is that Yin and Yang interact, stirring residual pathogens, while the patient's Zheng Qi was originally deficient, allowing the pathogens to adhere. Otherwise, how could the pathogens invade? Now, the disease recurs spontaneously because the Zheng Qi remains weak, and residual pathogens are stirred into activity. These are entirely due to internal factors, not external contractions; thus, it is similar to the Exchange disease. One also uses Shao Kun San to stabilize the Zheng Qi. Once the Zheng Qi is stabilized, the residual pathogens naturally recede.
Zhao Sizhen stated: In patients suffering from Shanghan, heat toxins latent in the Blood and Qi gradually dissipate through the exterior and interior. However, heat toxins latent in the Essence and Marrow have no outlet for excretion. Therefore, after recovery, if sexual intercourse occurs with a healthy person, transmission between men and women takes place, hence the name Yin-Yang Exchange, implying an exchange or transaction. After taking this powder, urination becomes smooth, the glans penis swells slightly, and the Yin toxin exits through the genital orifice.
Weng Kentang stated: When a man is ill and a woman contracts the disease through sexual intercourse, it is named Yang Yi (Yang Exchange); when a woman is ill and a man contracts the disease through sexual intercourse, it is named Yin Yi (Yin Exchange). If a man is infected, the scrotum swells, and pain radiates into the abdomen causing colic. If a woman is infected, there is lower abdominal urgency, with pain connecting the waist and hips to the interior of the abdomen.
Ke Qin stated: This syndrome lacks both internal and external etiologies and is fundamentally not Shanghan. It is labeled under Shanghan only to trace its origin. There are no exterior symptoms such as aversion to cold and fever, nor interior symptoms such as gastric excess and spontaneous diarrhea. Because sexual desire is uncontrolled, Yin pathogens find an opening to invade, transferring the harm to the previously healthy person. This instantly causes the essence, Qi, form, and spirit of the whole body to suffer from the damage of lustful fire. Thus, the person does not fall ill from Shanghan but from the Yin-Yang Exchange.