病源伤寒阴阳易病者，是男子妇人伤寒病新瘥未平复而与之交接得病者，名为阴阳易也
其男子病新瘥未平复，而妇人与之交接得病者，名阳易，其妇人得病新瘥未平复，而男子与
之交接得病者，名阴易，若二男二女并不相易，所以呼为易者，阴阳感动，其毒度着于人如
换易也，其病之状，身体重，小腹里急，或引阴中拘挛，热上冲胸，头重不能举，眼内生
，四肢拘急，小腹 痛，手足拳，皆即死，其亦有不即死者，病苦小腹里急，热上冲胸，头
重不能举，百节解离，经脉缓弱，血气空虚，骨髓枯竭，便嘘嘘吸吸，气力转少，着床不能
动摇，起止仰人，或引岁月方死。（出第八卷中）
深师疗妇人得温病虽瘥平复未满一百日，不可与交合，交合为阴易之病，病必拘急手
足拳皆死，丈夫病以易妇人，名为阳易，速当疗之可瘥，满四日，不可疗也，宜令服此药方。
干姜（四两）
上一味捣末，汤和，一顿服，温覆汗出得解，止手足伸遂愈。（范汪同出第十四卷中）
范汪 鼠粪汤，疗伤寒病后，男子阴易方。
薤（一大把） 鼠粪（十四枚）
上二味，以水五升，煮取二升，尽饮之，温卧汗出便愈，亦理劳复。（ 鼠屎两头尖者
是也肘后薤作蓝）
又丹米汤，疗伤寒病已后，男子阴易方。
丹米（三两）
上一味末，以薄酒和尽饮之，温覆汗出便愈，亦随人大小，不必三两，自以意消息之。
又疗交接劳复卯肿，腹中绞痛便绝死，竹皮汤方。
刮青竹皮（一升）
上一味，以水三升，煮五六沸，绞去滓，顿服立愈。（肘后同）
又疗阴阳易，栝蒌汤方。
栝蒌根（二两）
上一味，以水五升，煮取一升，分二服，先以青淡竹沥一升，合水二升，煮好银二两，
减半去银，先与病患饮之讫，须臾乃服汤，小便利即瘥，栝蒌汤银汁须冷服。（与前疗渴方
同）
千金曰昔者有人得伤寒病，已瘥未健，诣华敷视脉，敷曰∶虽瘥尚虚未复。阳气不足
，勿为劳事，余劳尚可，御内即死，临死当吐舌数寸，其妻闻其夫病除，从百余里来省之，
止宿交接，中间三日发病，口舌出数寸而死，病新瘥未满百日，气力未平复，而以房室者，
略无不死，有士盖正者，病愈后六十日，已能行射猎，以房室则吐涎而死，及热病房室，名
为阴阳易之病，皆难疗多死，近者有士大夫，小得伤寒，瘥已十余日，能乘马行来，自谓平
复，以房室则小腹急痛，手足拘挛而死，医者张苗说，有婢得病后数十日，有六人奸之皆死，
妇人
取女人中 近隐处烧取灰。
上一物为散，服方寸匕，日三，小便即利，阴头微肿，此为愈矣，女人病可取男子 如
前法，酒水服。（此本仲景方肘后同）
又疗交接劳复，卯肿缩，腹中绞痛，便欲死者方。
取交接妇人衣服以覆男子。（肘后同）
又方
取女人手足爪二十枚，女人衣中裳一尺烧。
上二味末，以酒服，亦可米汁饮服之。（出第十卷中肘后同）
Background Information:
Book Title: Waitai Miyao (Secret Essentials from the Outer Cabinet)
Author: Wang Tao
Dynasty: Tang Dynasty, Tianbao 11th Year
Chapter: Eight Formulas for Yin-Yang Exchange in Shanghan (Cold Damage)
Category: Formulas
[Translation]
The so-called "Yin-Yang Exchange" disease in Shanghan refers to a condition contracted by a man or woman after newly recovering from Shanghan but before full physical restoration, through sexual intercourse with the opposite sex. This disease is named "Yin-Yang Exchange."
If a man has newly recovered and not yet stabilized, and a woman engages in sexual intercourse with him contracting the disease, it is called "Yang Exchange." If a woman has newly recovered and not yet stabilized, and a man engages in sexual intercourse with her contracting the disease, it is called "Yin Exchange." If two men or two women interact, they do not exchange the disease. It is called "Exchange" because the Qi of Yin and Yang mutually resonate, and its pathogenic toxin transfers and attaches to another person, much like changing clothes. The symptoms of this disease include: heaviness of the body, urgency and pain in the lower abdomen, sometimes drawing the yin organs into spasms, heat rushing up to the chest, heaviness of the head making it difficult to lift, opacity inside the eyes, spasticity and stiffness in the four limbs, cramping pain in the lower abdomen, and curling of the hands and feet into fists. When these conditions appear, death usually follows; however, some patients do not die immediately. They suffer from urgency and pain in the lower abdomen, heat rushing up to the chest, heaviness of the head making it difficult to lift, a sensation that all joints are separating, slackness and weakness of the meridians, emptiness of blood and Qi, depletion of bone marrow, weak and rapid breathing (shushu xixi), gradual loss of strength, inability to move while lying in bed, requiring assistance from others to rise and walk, and some may drag on for months before dying. (From Volume VIII)
Shen Shi Fang treats women who have recovered from Wenbing (Warm Disease) but are within one hundred days of recovery; they must not engage in sexual intercourse. If they do, they contract the "Yin Exchange" disease, which inevitably leads to death due to spasticity and curling of the hands and feet. If a husband's disease is transmitted to his wife, it is called "Yang Exchange." It should be treated promptly to achieve recovery; if more than four days pass, it cannot be treated. It is appropriate to administer the following formula:
Ganjiang (Dried Ginger, Rhizoma Zingiberis Preparatum) (4 liang)
Grind the single herb into powder, mix with hot water, and take in one dose. Cover with blankets to induce sweating for relief; once the hands and feet extend, recovery is complete. (Fan Wang agrees; From Volume XIV)
Fan Wang's Shufen Tang (Rat Feces Decoction) treats men suffering from "Yin Exchange" after Shanghan.
Xie (Scallion Bulb, Allii Fistulosi Bulbus) (one large handful)
Shufen (Rat Feces, Mus Sordidus) (14 pieces)
Boil the two ingredients in 5 sheng of water until reduced to 2 sheng. Drink all of it. Lie warm to induce sweating for recovery. This also treats Laofu (relapse due to overexertion). (Note: Use rat feces with pointed ends; Zhouhou uses Lancao/Isatis Leaf instead of Xie).
Another formula, Danmi Tang, treats men suffering from "Yin Exchange" after Shanghan.
Danmi (Red Rice/Polished Red Rice, Oryza Sativa Rubra) (3 liang)
Grind the single ingredient into powder, mix with thin wine, and drink completely. Cover with blankets to induce sweating for recovery. Dosage can be adjusted according to the patient's size; 3 liang is not fixed. Adjust as appropriate.
Another formula treats relapse due to sexual intercourse accompanied by scrotal swelling and severe abdominal colic leading to near-death states, using Zhupi Tang (Bamboo Peel Decoction).
Qingzhupi (Green Bamboo Peel, Cortex Bambusae Viridis) (1 sheng)
Boil the single ingredient in 3 sheng of water for five to six boils. Strain out the dregs and take in one dose for immediate recovery. (Same as Zhouhou).
Another formula treats Yin-Yang Exchange using Gualou Tang (Trichosanthes Root Decoction).
Gualougen (Trichosanthes Root, Radix Trichosanthis) (2 liang)
Boil the single ingredient in 5 sheng of water until reduced to 1 sheng. Divide into two doses. First, take 1 sheng of Qingdan Zhuli (Clear Light Bamboo Sap) mixed with 2 sheng of water, boiled with 2 liang of good silver until the volume is halved, then remove the silver. Give this liquid to the patient first. After a short while, administer the herbal decoction. Recovery occurs when urination becomes smooth. The Gualou Tang with silver juice must be taken cold. (Same as the previous formula for thirst).
Qianjin Fang records: In the past, someone suffered from Shanghan. Although he had recovered, he was not fully robust. He sought pulse diagnosis from Hua Fu. Hua Fu said, "Although you appear recovered, you are still deficient and not restored. Your Yang Qi is insufficient. Do not engage in strenuous activities. General labor is acceptable, but sexual intercourse will cause death. Upon death, your tongue will protrude several inches." His wife, hearing of his recovery, traveled over a hundred li to visit him. She stayed overnight and engaged in intercourse. Three days later, he developed symptoms, his tongue protruded several inches, and he died. Anyone engaging in sexual intercourse within one hundred days of new recovery, before their Qi and strength have stabilized, will almost certainly die. A man named Shi Gaizheng, sixty days after recovery, was able to walk, shoot, and hunt, but died vomiting saliva after engaging in sexual intercourse. Also, engaging in sexual intercourse during febrile illness is called "Yin-Yang Exchange," which is difficult to treat and often fatal. Recently, a scholar-official suffered mild Shanghan. Ten days after recovery, he could ride a horse and walk, believing himself fully restored. He engaged in sexual intercourse, resulting in urgent lower abdominal pain, spasticity of the hands and feet, and death. Physician Zhang Miao stated that a maid-servant, dozens of days after her illness, had sexual relations with six men, and all six died.
For women suffering from this disease, take ash from burning the area near the female genitals.
Process the single substance into a powder. Take one fangcun bi (a measure roughly the size of a square inch) per dose, three times daily. Urination will become smooth, and slight swelling of the glans penis/vulva indicates recovery. For women suffering from this disease, take ash from the corresponding male area and administer as above, using wine or water. (This formula originally comes from Zhang Zhongjing; same as Zhouhou).
Another formula treats relapse due to sexual intercourse, with scrotal swelling/shrinking and severe abdominal colic leading to near-death states.
Take the clothing worn by the woman during intercourse and use it to cover the man. (Same as Zhouhou).
Another formula:
Take twenty nails/claws from a woman's hands and feet, and one chi of her inner skirt. Burn them.
Grind the two substances into powder. Administer with wine, or alternatively with rice juice. (From Volume X; same as Zhouhou).