肾之为脏水，脏也，水居北方，天一生之，故受气之初，先生两肾左为肾而属水，
右为命门而属火，所谓非水不生，非火不成，水火相济。阴阳之征兆也。然肾在俯
下，痘疹之初，耳独凉者，膀胱为肾腑，肾不受邪耳，此克能存水之德，以制阳光者
也。如耳反热则水不能制火，将有世所谓归脏之虞矣。治宜抑枭炎，资肾水，况阳常有
余，阴常不足，故每有真水既亡，津液暴脱，则其气滞其发燥，而乃 乎不能润乎
皮毛，滋乎腠理，痘中之血亦干而变黑矣。黑者火燥水涸，而血干之色也。腰痛者，毒
火亢害之征也。此理之常，虽曰黑属癸水，岂可拘以肾实为邪而泻哉。夫变黑腰痛之
症，本属火盛热极，经所谓亢则害也。外火灼于肌肤之间，故其色黑，火毒相亢，而玄
水枯竭，故腰疼耳。其痘必干枯，或多斑点，非红则紫，非紫则黑，其属火也，明
矣。治法大宜升提表散，而兼清凉解毒，于见点之初，使热毒得解，斑紫得清，正痘得
见，然后调理气血，庶可挽回，若斑不退，紫不清，痘伏隐隐而不起，腰疼阵阵而难
伸，头面预肿，腹胀喘粗者、是必痘终不起，而难冀其有生也，至有痘将成就，而忽
变黑倒靥者，是亦血热火亢，毒滞血干而成，内攻为逆候也。故庄氏曰∶斑疮倒靥而
黑色者，是谓鬼疮，此恶之之词也。若是所谓冬月盛寒归肾，变黑之说者，岂理也哉，
肾脏作为水脏，位于身体下部。水对应北方，由“天一生水”所化生。因此，在生命受气之初，先生成两肾：左侧为肾，属性为水；右侧为命门，属性为火。这就是所谓的“没有水就无法生长，没有火就无法成形”，水火相互济助，是阴阳的征兆表现。
然而，肾脏位置在下部。痘疹（天花/麻疹类疾病）初期，如果耳朵唯独发凉，这是因为膀胱是肾的腑，肾未受邪气侵袭，这体现了肾能够保存其水的德行，从而制约阳热之气。如果耳朵反而发热，说明水不能制约火，将会有世人所说的“归脏”（毒气内陷脏腑）的危险。治疗应当抑制亢盛的火热，资助肾水。况且阳气常有盈余，阴精常显不足，所以往往出现真水枯竭、津液突然脱失的情况，导致气机阻滞，皮肤毛发失去润泽，腠理得不到滋养，痘疮中的血液也会干枯而变成黑色。黑色是火燥水干、血液干枯的颜色。腰痛是毒火亢盛危害身体的征象。这是常理，虽然黑色归属于癸水（肾水），但岂能拘泥于认为这是肾实证邪气而使用泻法呢？
变黑伴腰痛的病症，本属于火盛热极，正如经典所说“亢盛则有害”。外部的火热灼烧肌肤之间，所以颜色变黑；火毒相互亢盛，导致肾水枯竭，所以出现腰痛。痘疮必定干枯，或者斑点较多，不是红色就是紫色，不是紫色就是黑色，这明显属于火证。治疗方法非常适宜采用升提透表发散的方法，并兼用清凉解毒之法。在痘点刚出现的时候，使热毒得以解除，紫斑变得清透，正常的痘疮显现出来，然后调理气血，或许可以挽回生机。如果斑点不退去，紫色不清透，痘疮隐伏不起，腰痛阵阵难以伸展，头面部预先肿胀，腹部胀满呼吸急促粗重，那一定是痘疮最终无法起发，很难期望有生存的希望了。至于痘疮即将成熟时，忽然变黑并倒靥（痘疮凹陷不结痂或塌陷），这也是血热火亢、毒滞血干所致，毒气内攻属于逆证。所以庄氏说：“斑疮倒靥且呈黑色的，称为鬼疮”，这是厌恶它的说法。像那种说是冬天严寒导致毒气归肾、变黑的说法，难道是合理的吗？
The Kidney is a Water Zang organ. Water corresponds to the North, originating from "Heaven generates One (Water)." Thus, at the initial stage of receiving Qi, two Kidneys are formed: the left is the Kidney, belonging to Water; the right is the Mingmen (Gate of Life), belonging to Fire. This is referred to as "without Water, there is no growth; without Fire, there is no formation," where Water and Fire mutually support each other, representing the manifestation of Yin and Yang.
However, the Kidney is located inferiorly. At the onset of variola (smallpox/varioloid), if only the ears are cold, it is because the Bladder is the Fu organ of the Kidney, and the Kidney has not been invaded by pathogenic factors. This demonstrates the Kidney's ability to preserve its Water virtue to control Yang heat. If the ears become hot instead, it indicates that Water fails to control Fire, leading to the danger known as "returning to the Zang organs" (internal collapse of toxins). Treatment should aim to suppress rampant fire and nourish Kidney Water. Moreover, Yang often has excess while Yin is frequently deficient. Consequently, true Water may be exhausted, and body fluids suddenly depleted, causing Qi stagnation. The skin and hair lose moisture, and the interstices (couli) fail to receive nourishment. The blood within the pox becomes dry and turns black. Blackness is the color of dried blood resulting from fiery dryness and water depletion. Lower back pain is a sign of excessive toxic fire harming the body. This is a common principle. Although black belongs to Gui Water (Kidney Water), one cannot rigidly adhere to the notion of Kidney Excess syndrome and apply purgative methods.
The condition of blackening accompanied by lower back pain essentially stems from extreme heat and flourishing fire, as stated in the classics: "Excess leads to harm." External fire scorches the skin and flesh, causing black discoloration; the mutual excess of fire and toxin depletes the profound Water (Kidney Yin), resulting in lower back pain. The pox will inevitably be dry and withered, or present with numerous macules/papules, appearing either red or purple, or purple turning black. This clearly indicates a Fire pattern. The treatment method should primarily employ lifting and dispersing techniques to release the exterior, combined with cooling and detoxifying approaches. At the initial appearance of the spots, allowing the heat-toxin to resolve and the purple macules to clear, so that normal pox can emerge, followed by regulating Qi and Blood, may salvage the patient. However, if the macules do not recede, the purple hue does not clear, the pox remains hidden and fails to erupt, lower back pain persists making extension difficult, the head and face swell prematurely, and abdominal distension with coarse breathing occurs, it implies the pox will ultimately fail to rise, and survival is unlikely. Furthermore, if the pox, nearing maturity, suddenly turns black and undergoes inversion (inverted eruption/collapse), this is also caused by blood heat and hyperactive fire, where toxin stagnation dries the blood, constituting an adverse internal attack. Therefore, Zhuang stated: "Macules and papules with inverted eruption presenting in black are called 'Ghost Sores'," which is a term expressing aversion. Is the theory that severe winter cold causes toxins to return to the Kidney and turn black reasonable?