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The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: "Obstruction in the Two Yang meridians is called Xiao (Wasting and Thirsting)." Li Dongyuan said: "The Two Yang refers to the Yangming meridians. The Hand-Yangming Large Intestine meridian governs body fluids; if affected by heat, it causes yellow eyes and thirst, indicating a deficiency of body fluids. The Foot-Yangming Stomach meridian governs blood; if affected by heat, it causes excessive hunger after eating, due to latent fire in the blood leading to a deficiency of blood. 'Obstruction' refers to the accumulation of heat. Although the Three Xiao diseases are divided into Upper, Middle, and Lower, their origin lies in the Stomach Earth. As the repository of all grains, the Stomach receives everything. Foods that are fried, roasted, or grilled, as well as excessive consumption of rich wine, assist stomach fire and deplete body fluids. If the pathogen transmits to the Qi level, it becomes Upper Xiao; if it transmits to the Blood level, it becomes Lower Xiao.

If sexual activity is regulated and Yin energy is not damaged, the dryness-heat remains only in the Stomach meridian, manifesting merely as excessive hunger after eating. Upper Xiao involves the Lung, presenting with a red and cracked tongue surface and extreme thirst for drinking. This occurs because stomach fire first transmits to the Lung, followed by Heart fire. The Classics state: 'When Heart transfers heat to the Lung, it transforms into Ge Xiao (Diaphragmatic Wasting-Thirst).' This describes the most severe manifestation, but essentially, it originates from stomach fire. Middle Xiao involves the Stomach, presenting with a good appetite yet frequent hunger, spontaneous sweating, hard stools, and frequent urination, sometimes accompanied by dry mouth and desire to drink, though these symptoms are less severe than those of Upper or Lower Xiao. Currently, physicians treat this condition using Ganlu Yin (Sweet Dew Decoction). While there is some rationale, nourishing Yin and tonifying blood is somewhat secondary; clearing heat and generating fluids is more urgent. Chaihu Shaoyao Tang (Bupleurum and Peony Decoction) is indeed an excellent prescription. Zhang Zhongjing, in his *Shanghan Lun* (Treatise on Cold Damage), stated: "For thirst caused by wind-fever, resolve it through dietary management." This indicates that thirst is not solely caused by stomach fire but also by wind-heat from the Liver and Gallbladder attacking the body. Relying solely on herbs cannot bring about a rapid cure; one must frequently consume sugarcane juice and pear juice through diet to avoid death. This is also a wonderful method for treating Xiao-Kel (Wasting-Thirst Syndrome). (This statement reflects accurate clinical experience, not empty exaggeration.)

Lower Xiao involves the Kidney, presenting with withered and dry earlobes and urine resembling paste. There is profound medical logic hidden here, unknown to ordinary people. Urine resembling paste seems to indicate Kidney deficiency, and treating it with cooling herbs is ineffective. In fact, in Ren Xiao (Kidney Wasting-Thirst), not only does stomach heat flow downward, but the Yang fire of the Heart also descends toward the Kidney. It is appropriate to use Danggui Liu Huang Tang (Angelica Sinensis and Six Yellow Decoction) or Liuwei Dihuang Wan (Six-Ingredient Rehmannia Pill), adding Rhinoceros Horn (Xi Jiao) to clear Heart fire, so that the wasting-thirst may heal. If one sees seminal emission and dares not use cooling herbs, would that not be a mistake? *Zonglu* states: "Those who have not yet developed polyphagia will inevitably develop brain carbuncles or back sores, due to excessive evil fire. Those who cannot eat will inevitably develop abdominal distension and bloating, because treatment was too aggressive, leaving upper heat unresolved while middle cold arises." Qibo said: "If the pulse is excess and the disease has lasted long, it is treatable; if the pulse is wiry and small and the disease has lasted long, it is untreatable." This is because a surging and rapid pulse indicates excess evil fire with still-intact body fluids. If the pulse is fine and weak, it means body fluids are exhausted and Stomach Qi is perished, hence untreatable. If medication is unavoidable, it is suitable to add Ginseng (Renshen) to Chaihu Shaoyao Tang. In severe cases, Bawei Dihuang Wan (Eight-Ingredient Rehmannia Pill) might revive the dying.

Chaihu Shaoyao Tang (Bupleurum and Peony Decoction)
Ingredients: Chaihu (*Bupleuri Radix*), Huangqin (*Scutellariae Radix*), Huafen (*Trichosanthis Radix*), Gancao (*Glycyrrhizae Radix et Rhizoma*), Baishao (*Paeoniae Radix Alba*), Maidong (*Ophiopogonis Radix*), Zhimu (*Anemarrhenae Rhizoma*), Huanglian (*Coptidis Rhizoma*).
Upper Xiao and Middle Xiao are diseases of the Qi level; one should not abruptly use blood-tonifying herbs. This formula is most suitable. Additionally, drinking clam decoction daily yields great efficacy. For Middle Xiao with constipation, remove Huanglian from this formula and add Dahuang (*Rhei Radix et Rhizoma*) to gently promote bowel movement.

Ganlu Yin (Sweet Dew Decoction)
Ingredients: Tiandong (*Asparagi Radix*), Maidong (*Ophiopogonis Radix*), Shengdi (*Rehmanniae Radix*), Shudi (*Rehmanniae Radix Preparata*), Yinchend (*Artemisiae Scopariae Herba*), Pipaye (*Loquat Leaf*), Huangqin (*Scutellariae Radix*), Yiren (*Coicis Semen*, Coix Seed), Shihu (*Dendrobii Caulis*), Gancao (*Glycyrrhizae Radix et Rhizoma*), Shanzhi (*Gardeniae Fructus*).
Another version omits Yinchend and Shanzhi, using Zhike (*Aurantii Fructus Immaturus*) instead.

Danggui Liu Huang Tang (Angelica Sinensis and Six Yellow Decoction)
Ingredients: Danggui (*Angelicae Sinensis Radix*), Huangqi (*Astragali Radix*), Huangqin (*Scutellariae Radix*), Huanglian (*Coptidis Rhizoma*), Huangbai (*Phellodendri Cortex*), Shengdi (*Rehmanniae Radix*), Shudi (*Rehmanniae Radix Preparata*).