阴阳易者，因瘥后交合，而无病之人反得病者是也。其候大便不通，心神昏乱，惊
惕不安，体重少气，少腹里急，及引阴中拘挛，热上冲胸，头重不欲举，眼中生花，膝
胫拘急是也。然肾经亏败，真阳虚损，故有寒无热，脉虚足冷，宜人参四逆汤，调下烧
散，阴头微肿则愈。若妇人病未平，复有犯房事，小腹急疼，腰膝俱痛，四肢不仁，
无热者，当归白术散。凡阴阳易，极难调理，须分寒热施治，舌出数寸者死。
伤寒愈后浮肿，若因水气者，宜利之。若胃虚食少者，宜五苓散加苍术、陈皮、木
香、砂仁之类。胃不虚者，以商陆一味，煮粥食之，亦妙。伤寒大病瘥后足肿者，不
妨。但节饮食，戒酒色，胃气强，肿自消也。
伤寒汗下不彻，余邪结在耳后一寸二三分，或两耳下俱硬肿者，名曰遗毒，宜速消
散，缓必成脓，以连翘败毒散治之。如项肿痛，加威灵仙；大便实加大黄、穿山甲。如
发肿有脓不消，或已破未破者，但用内托消毒散，加角刺、升麻、金银花、甘草之类。
然古人方书之论如此，但实多由于久热伤阴，盖少阳少阴，阴亏已极，因乃虚火上
冲，所以腮颊耳后肿痛也。《经》曰∶荣气不从，逆于肉里，乃生痈肿。况耳后方圆一
寸皆属于肾，有何毒之谓欤？治宜以滋阴化痰，散郁和肝而肿自愈。如熟地、麦冬、土
贝母、生白芍、甘桔、连翘之类，略佐青皮、柴胡少许足已。若尺脉甚弱者，竟用上
病疗下之法，投以引火归源之药，则肿不治而自散。若误认以毒为事而攻之，不惟肿
结，愈固而愈甚，必致变生别病而危矣。此张之鄙见也。
阴阳易病，是指伤寒病初愈时进行房事，原本没有生病的一方反而染上疾病的情况。其症状表现为大便不通，心神昏乱，惊恐不安，身体沉重且气息短少，小腹部拘急疼痛，并牵引至阴部痉挛，热气上冲胸部，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。这是因为肾经亏损败坏，真阳虚损，所以只有寒象而没有热象，脉象虚弱，脚部发冷，适宜服用人参四逆汤，配合烧散（将患者衣物烧灰制成的药散）调服，若阴头轻微肿胀则病愈。如果是女性患者在病未痊愈时再次犯房事，出现小腹部急痛，腰部和膝盖都疼痛，四肢麻木不仁，没有发热症状的，适用当归白术散。凡是阴阳易病，极难调理，必须区分寒证和热证来施治，如果舌头伸出数寸长不能收回的，预后不良，会死亡。
伤寒病好后出现浮肿，如果是由于水气停留引起的，适宜采用利水的方法治疗。如果是胃气虚弱、饮食减少的，适宜用五苓散加入苍术、陈皮、木香、砂仁等药物。胃气不虚的，单用商陆一味药煮粥食用，效果也很好。伤寒大病初愈后出现足部浮肿的，不必过于担心。只要节制饮食，戒除酒色，胃气强壮起来，浮肿自然就会消退。
伤寒经过发汗或攻下治疗后病邪未除尽，残余的病邪结聚在耳后一寸二三分处，或者双耳下方都坚硬肿胀的，称为遗毒，应当迅速消散，拖延必定化脓，用连翘败毒散治疗。如果颈部肿痛，加入威灵仙；如果大便秘结，加入大黄、穿山甲。如果已经发生肿胀且有脓液但不消散，或者已经破溃或未破溃的，只使用内托消毒散，加入皂角刺、升麻、金银花、甘草等药物。然而古人的方书论述如此，但实际上多是由于长期高热损伤阴液，导致少阳经和少阴经阴液极度亏虚，因而是虚火上冲，所以导致腮颊和耳后肿痛。《黄帝内经》说：营气运行不畅，逆乱于肌肉纹理之间，就会生成痈肿。况且耳后方圆一寸的区域都属于肾脏管辖，哪里有什么“毒”可言呢？治疗应当以滋阴化痰、疏散郁结、调和肝脏为主，这样肿胀自然会痊愈。如熟地黄、麦冬、土贝母、生白芍、甘草桔梗、连翘等药物，稍微佐以少量的青皮、柴胡就足够了。如果尺脉非常微弱，完全可以使用治疗上部疾病而兼顾下部的方法，投用引火归源的药物，那么肿胀不用专门治疗也会自行消散。如果错误地认为这是毒邪而加以攻伐，不仅肿胀无法消除，反而会更加坚固严重，必然导致产生其他病变而危及生命。这是我的浅陋见解。
Yinyang Yi (Exchange of Yin and Yang) refers to the condition where a healthy person contracts the disease after sexual intercourse with a patient recovering from Shanghan (Cold Damage). The manifestations include constipation, mental confusion, fright and restlessness, heavy body with shortness of breath, urgency and tension in the lower abdomen extending to spasms in the genitalia, heat rushing up to the chest, heaviness of the head making one unwilling to lift it, visual disturbances such as seeing spots, and stiffness and cramping of the knees and calves. This occurs because the Kidney meridian is depleted and damaged, and the True Yang is deficient; thus, there are cold signs without heat signs, a deficient pulse, and cold feet. It is appropriate to administer Renshen Sini Tang (Ginseng and Aconite Decoction), taken with Shaosan (Burnt Powder, made from burning the patient's clothing), and if the glans penis swells slightly, the disease will resolve. If a female patient engages in sexual activity before her illness has fully resolved, presenting with urgent pain in the lower abdomen, pain in both the waist and knees, numbness in the four limbs, and no fever, Danggui Baizhu San (Angelica Sinensis and Atractylodes Macrocephala Powder) should be used. Yinyang Yi is extremely difficult to regulate; treatment must distinguish between cold and heat patterns. If the tongue protrudes several inches and cannot be retracted, the prognosis is fatal.
Edema occurring after the recovery from Shanghan: if caused by water qi retention, diuresis is indicated. If due to deficiency of Stomach Qi and poor appetite, Wuling San (Five-Ingredient Poria Pill) added with Cangzhu (Atractylodis Rhizoma), Chenpi (Citri Reticulatae Pericarpium), Muxiang (Aucklandiae Radix), and Sharen (Amomi Fructus) is suitable. If Stomach Qi is not deficient, consuming porridge boiled with a single herb, Shanglu (Phytolaccae Radix), is also effective. Foot edema following severe Shanghan is not alarming. As long as diet is regulated, and alcohol and sexual indulgence are abstained from, once Stomach Qi strengthens, the edema will subside spontaneously.
When Shanghan is not fully resolved through sweating or purging, residual pathogenic factors may knot in the area one cun two fen three li behind the ear, or cause hardness and swelling below both ears. This is named Weidu (Residual Toxin). It should be dispersed quickly; delay will lead to suppuration. Lianqiao Baidu San (Forsythia Decoction for Resolving Toxins) is indicated. If there is swelling and pain in the neck, add Weilingxian (Syringae Ramulus et Folium); if stool is hard, add Dahuang (Rhei Radix et Rhizoma) and Chuanshanjia (Manis Squama). If swelling persists with pus formation, whether broken or unbroken, Neituo Xiaodu San (Internal Support and Detoxification Powder) added with Jiaoci (Gleditsiae Spina), Shengma (Cimicifugae Rhizoma), Jinyinhua (Lonicerae Japonicae Flos), and Gancao (Glycyrrhizae Radix et Rhizoma) should be used. However, although ancient texts describe it this way, in reality, it is mostly due to prolonged high fever injuring Yin fluids. The Shaoyang and Shaoyin meridians suffer extreme Yin deficiency, leading to deficient fire rushing upward, causing swelling and pain in the cheeks and behind the ears. The Classic states: "When Ying Qi does not follow its course and reverses into the flesh, carbuncles and swellings arise." Moreover, the area round one cun behind the ear belongs to the Kidney; what toxin could there be? Treatment should focus on nourishing Yin, resolving phlegm, dispersing stagnation, and harmonizing the Liver, so that the swelling heals itself. Herbs such as Shudi (Rehmanniae Radix Preparata), Maidong (Ophiopogonis Radix), Tubei Mu (Fritillariae Thunbergii Bulbus), Sheng Baishao (Paeoniae Radix Alba), Gancao (Glycyrrhizae Radix et Rhizoma), Jiegeng (Platycodonis Radix), and Lianqiao (Forsythiae Fructus) can be used, with small amounts of Qingpi (Citri Reticulatae Pericarpium Viride) and Chaihu (Bupleuri Radix) as adjuvants. If the Chi pulse (cun position at the wrist corresponding to the Kidney) is very weak, the method of treating the upper by addressing the lower should be employed, using herbs that guide fire back to its source, allowing the swelling to disperse without direct treatment. If mistakenly treated as a toxic accumulation and attacked with harsh purgatives, the swelling will not only persist but worsen, potentially leading to other critical conditions. This is my humble opinion.