孙真人论曰。妇人温病虽瘥。未能平复。血脉未和。尚有热毒。
足以毒人。男子接之得病。名为阴易之病。其人身体重。热上冲胸。
头重不能举。眼中生眵 。（一作膜脉）四肢（一云膝胫）拘急。小腹
绞痛。手足拳。皆即死。其亦有不即死者。病苦小腹里急。热上中胸。
头重不能举。百节解离。经脉缓弱。血气虚。骨髓竭。便嘘嘘吸吸。气
力转少。着床不能动摇。或引岁月方死。晋代名医张黄。言有婢得
病。瘥后数十日。有六人接之。皆死。可不戒之。
仲景曰。伤寒阴阳易之为病。其人身体重。少气。小腹里急。或
引阴中拘挛。热上冲胸。头重不能举。眼中生花。（一作眵。千金翼加
胞赤二字。）膝胫拘急者。烧 散主之。
千金方曰。交接劳复。阴卵肿缩。宜取妇人衣服以覆男子。
庞氏曰。阴阳交易。阴阳相感动。其毒瓦斯着人。如换易也。男子
病新瘥。妇人与之交。妇人得病。名曰阳易。妇人病新瘥。男子与之
交。男子得病。名曰阴易。若二女二男。则不相易。然女犯男得病。鲜
有死者。男犯女得病。治稍缓则死。无一生者。又若女犯男而男自劳
复。则女不病。男犯女而女自劳复。则男得病亦轻。富贵之家。虽知
其事。后生忽恣意犯之。多致不救。田野之家。蒙蒙昧昧。只知伤寒
能杀人。因此死者。又十有三四。皆不知其所犯之由。深可伤也。宜
服手足甲 灰散。阴头毛际二穴灸之。男女初得病者。便服薤根鼠
屎汤。出汗愈。灸阴头百壮。而卵缩未下者。灸大敦二穴小炷七壮。
足大拇趾旋毛上是穴。
活人书曰。阴阳易病。男子则体重少气。阴肿入腹。绞痛。妇人
则里急。腰胯连腹内痛。余与仲景孙氏庞氏三家同。
又曰。烧 散、
鼠屎汤、竹叶汤、干姜汤、竹茹汤、当归白术汤。皆可选用。雍曰。
男子用千金赤帛烧散为奇。
雍曰。男子初病伤寒。其毒虽未必重。及其易人。则多杀人。过
于本伤何哉。盖本病所感。必先太阳膀胱经。自表入里。其传有渐。
易人之病。随感而入。直伤膀胱与肾五脏。不由经脉。故其病只见里
症。无表症。病在脏不在经也。至其所用药。必须隐秽之物。与本脏
相侵者。然后可败而逐之。至于灸法。亦必在隐恶之处。盖病不在经
络之中。不可取也。
Sun Simiao stated: Although a woman's warm disease (Wenbing, 温病) symptoms have subsided, she has not fully recovered, her blood vessels are not harmonized, and heat-toxin (Redu, 热毒) remains. This toxin is sufficient to infect others. If a man engages in sexual intercourse with her and contracts the disease, it is called "Yin Yi" (Yin Exchange, 阴易). The patient experiences heavy body sensation, heat rushing up to the chest, heaviness of the head making it difficult to lift, excessive eye discharge (or eye membrane), spasm and stiffness of the four limbs (or specifically knees and shins), severe colic pain in the lower abdomen, and curling of hands and feet into fists. This condition usually leads to immediate death; however, some do not die immediately. Their suffering involves urgency and tightness in the lower abdomen, heat rushing to the chest, inability to lift the head due to heaviness, a feeling of joints separating, slack and weak meridians, deficiency of blood and qi, exhaustion of bone marrow, labored breathing (shushing inhalation/exhalation), decreasing strength, inability to move while lying in bed, and some may die after months. Zhang Huang, a famous physician of the Jin Dynasty, said that a maid contracted a disease, and dozens of days after recovery, six men engaged in intercourse with her, all of whom died. Should one not be vigilant about this?
Zhang Zhongjing stated: In the disease of Yin-Yang Exchange following cold damage (Shanghan, 伤寒), the patient suffers from heavy body sensation, shortness of breath, urgency and tightness in the lower abdomen, sometimes with spasms extending to the yin organs, heat rushing up to the chest, heaviness of the head making it difficult to lift, and blurred vision (or excessive eye discharge; *Qianjin Yifang* adds "red eyelids"). For those with spasm and stiffness of the knees and shins, Shaokui San (Burned Underwear Powder, 烧裈散) is the primary treatment.
The *Essential Prescriptions Worth a Thousand Gold* (*Qianjin Fang*, 千金方) states: For relapse due to sexual activity, presenting with swelling and retraction of the scrotum, it is appropriate to cover the man with the woman's worn clothing.
Pang Anshi stated: Through yin-yang interaction and mutual stimulation, the pathogenic toxin attaches to the person, akin to an exchange. If a man whose illness has just resolved engages in intercourse with a woman, and the woman contracts the disease, it is named "Yang Yi" (Yang Exchange, 阳易). If a woman whose illness has just resolved engages in intercourse with a man, and the man contracts the disease, it is named "Yin Yi". If two women or two men engage in intercourse, no exchange occurs. However, when a woman infects a man, death is rare; when a man infects a woman, if treatment is delayed even slightly, death ensues, with no survivors. Furthermore, if a woman infects a man but the man subsequently relapses due to overexertion, the woman does not become ill; if a man infects a woman but the woman subsequently relapses due to overexertion, the man's illness will be milder. Wealthy families, though aware of these matters, often see young people indulging their desires and violating taboos, leading to untreatable conditions. Rural folk, ignorant and obscure, only know that cold damage can kill; thus, three or four out of ten deaths are due to this cause, without knowing the reason for their infection, which is deeply lamentable. It is advisable to take Shouzu Jia Hui San (Hand and Foot Nail Ash Powder, 手足甲灰散) and moxa-apply two acupoints at the base of the penis near the hairline. For both men and women newly afflicted, taking Xiegen Shoushi Tang (Scallion Root and Rat Dropping Decoction, 薤根鼠屎汤) to induce sweating leads to recovery. Moxa-apply one hundred zhu (units of moxa cone size) to the glans penis. If the testicles remain retracted, moxa-apply the Dacun (LR1, Great Rushing, 大敦) acupoint on both sides using small cones, seven zhu each. The acupoint is located where the hair whorl is on the big toe.
The *Liushiren Shu* (*Liu Ren Shu*, 活人书) states: In Yin-Yang Exchange disease, men present with heavy body sensation, shortness of breath, swelling of the yin organs retracting into the abdomen, and colic pain; women present with internal urgency, pain connecting the waist and hips to the inside of the abdomen. These views align with those of Zhang Zhongjing, Sun Simiao, and Pang Anshi.
It further states: Shaokui San, Shoushi Tang, Zhuye Tang (Bamboo Leaf Decoction, 竹叶汤), Ganjiang Tang (Dried Ginger Decoction, 干姜汤), Zhuru Tang (Bamboo Rind Decoction, 竹茹汤), and Danggui Baizhu Tang (Angelica and Atractylodes Macrocephala Decoction, 当归白术汤) can all be selected for use. Guo Yong remarked: Using the Chi Bo Shao San (Red Silk Burned Powder, 赤帛烧散) from *Qianjin Fang* for men is a remarkable approach.
Guo Yong stated: When a man initially contracts cold damage, the pathogenic factor may not be severe, but once transmitted to another person, it often causes death. Why is it more lethal than the original cold damage? Generally, the initial pathogen first invades the Taiyang Bladder Meridian (Taiyang Pangguang Jing, 太阳膀胱经), moving from the exterior to the interior with a gradual transmission process. In contrast, the disease transmitted through exchange enters directly upon infection, directly damaging the Bladder and Kidney viscera, bypassing the meridians. Therefore, the disease presents only with interior syndromes (Li Zheng, 里症) and no exterior syndromes (Biao Zheng, 表症); the pathology is in the viscera, not the meridians. Consequently, the medications used must be foul substances that interact with and counteract the specific viscera, thereby defeating and expelling the toxin. Similarly, moxibustion must be applied in hidden or foul areas. Because the disease is not within the meridians, standard meridian points cannot be selected.