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Head sweating is generally caused by the upward congestion of pathogenic heat, although cases of internal collapse of Yang Qi occasionally occur. The head is the meeting point of all Yang meridians; since the three Yin meridians do not ascend to the head, head sweating does not occur in Yin meridian diseases, thus head sweating belongs to Yang meridians. When sweat covers the whole body, it is called "Re Yue" (the dispersal of heat outward). If heat cannot disperse outward but instead steams upward into the Yang regions, causing Yang Qi to rush upward and body fluids to gather there, only the head sweats. Accompanying symptoms include heat binding internally as seen in Taiyang disease, fire coercion in Yangming disease, alternating chills and fever with pathogens half-exterior and half-interior, heat entering the blood chamber, empty irritability, fluid-binding chest fullness, jaundice, and blood stasis syndromes—all of which represent heat failing to disperse. Treatment methods involve either dispersing, harmonizing, clearing heat, or purging to eliminate the pathogen, after which the disease resolves spontaneously. In cases of head sweating due to Qi collapse, it is often caused by improper purging injuring Yin, excessive attacking methods, or continuous diarrhea, leading to exhaustion of Yin below and collapse of Yang above. With no urination and head sweating appearing above, the condition is critical. *Huo Ren Shu* (Manual of Saving Lives) advises caution against purging when head sweating occurs, whereas Zhang Jingyue's treatment entries for head sweating include the use of Chengqi Tang. At first glance, these seem contradictory, but careful study reveals both are correct. The caution against purging in *Huo Ren Shu* refers to patients with dry viscera, empty bladder, and scant body fluids. Zhang Jingyue, however, addresses patients with constipation, abdominal distension and pain accompanied by head sweating, for whom purging with Chengqi Tang is appropriate. Thus, whether to purge depends on the accompanying symptoms of head sweating. For head sweating with exterior pathogens and tight, rapid pulse requiring dispersal, Xiaochaihu Tang and various Chaihu decoctions are suitable (see *Jingyue Quanshu*, New Formulas, Dispersing Formulas). For head sweating with fire pathogens, surging and slippery pulse, and internal irritability and heat requiring clearing, Baihu Tang and Yiyuan San are suitable. These constitute the general principles for treating head sweating.

During sleep, Wei Qi (Defensive Qi) travels inside. With latent heat within and insecure exterior Yang Qi, body fluids leak out. Heat steams outward, pores open, and night sweats occur. Upon waking, Wei Qi moves to the exterior, and night sweats cease. Night sweats in miscellaneous diseases are attributed to Yin deficiency; night sweats in epidemics are caused by pathogens affecting the three Yang meridians. All three Yang meridians can present with night sweats, but pathogens at the half-exterior/half-interior level are most common, so harmonization is the primary treatment principle. Observing Zhang Zhongjing’s discussion on night sweats in combined Three Yang diseases, where drowsiness is emphasized, indicates heat in the Gallbladder meridian, treated primarily with Xiaochaihu Tang.