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The meridians of all Yang channels circulate on the head, while the three Yin channels reach the nape and return. Head sweating (Tou Han) occurs when pathogens contend with the Yang channels, causing sweat to appear on the head. If sweat covers the entire body, it is called "heat venting" (Re Yue). Now, since heat cannot vent outward but Yang Qi ascends, and body fluids gather upward, only the head sweats. When the interior is deficient, purgation is contraindicated; when internal fluids are depleted, diaphoresis is inadvisable. In cases of head sweating, further diaphoresis must not be applied. Conditions such as blood stasis in the interior, heat entering the Blood Chamber (Xue Shi), deficiency vexation with water accumulation, all cause head sweating. This results from heat constrained internally reaching upward; treatment involves emesis or purgation to expel the pathogen. If urination is difficult, and there is internal-external blockage leading to head sweating, it indicates collapse of Yang Qi (Yang Tuo). Misusing purgation on patients with dampness, resulting in forehead sweating with wheezing and difficulty urinating, or even if urination becomes free, also signifies collapse of Yang Qi. Both conditions are considered untreatable. *Bai Wen* states: Exterior excess with interior deficiency. Therefore, head sweating should not be treated with purgation.
Jaundice with head sweating stopping at the neck, difficulty urinating, and craving fluids indicate dampness; use Yinchen Hao Tang (Artemisiae Scopariae Decoction) or Yinchen Wuling San (Artemisiae Scopariae and Five-Ingredient Poria Powder).
Chest binding (Jie Xiong) in the heart region, palpitations and fullness without significant fever, and head sweating can be treated with Banxia Fuling Tang (Pinellia and Poria Decoction).
Delirium with head sweating indicates blood heat belonging to the Yangming channel; use Chengqi Tang (Chengqi Decoction). If there is profound stifling sensation in the chest with head sweating, use Zhizi Chi Tang (Gardenia and Fermented Soybean Decoction).
For half-exterior half-interior patterns with Chaihu syndrome, use Xiao Chaihu Tang (Minor Bupleurum Decoction). Alternating fever and chills with slight aversion to cold indicate an exterior pattern. Fullness under the costal margin and hard stool indicate an interior pattern.

The four limbs are the root of all Yang channels. Heat accumulating in the Stomach causes body fluids to distribute laterally to the hands and feet. Accumulated heat leads to restlessness and delirium; combined with cold, it leads to indistinguishability of food and water. This distinguishes the applications of Chengqi Tang from Lizhong Tang.
In Yangming disease, with sweating of the hands and feet, delirium, and difficulty defecating, administer Chengqi Tang. In Yangming cold-dampness, with inability to eat, difficulty urinating, sweating of the hands and feet, initially hard then loose stools, and indistinguishability of food and water, administer Lizhong Tang (Regulate the Middle Decoction). Alternatively, use Zhuling Tang (Polyporus Decoction).

Night sweating (Dao Han) refers to sweating during sleep that stops upon waking. For miscellaneous diseases, this is attributed to Yang deficiency; for Shanghan (Cold Damage), it is attributed to the half-exterior half-interior level, indicating heat in the Gallbladder.
In Yangming disease, with a floating-tight pulse, tidal fever, and night sweating, use Chaihu Guizhi Tang (Bupleurum and Cinnamon Twig Decoction). With a floating-large pulse, drowsiness, and sweating upon closing the eyes, use Xiao Chaihu Tang or Chaihu Guizhi Tang.