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The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: All pain, itching, sores, and ulcers belong to Heart Fire. Fire, as a substance, has the capacity to scorch and consume all things, causing various forms of destruction and decay. Generally speaking, when human skin or flesh is near fire, it causes burns; if the muscle is close to the fire, it causes pain; if slightly farther away, it causes itching. This is the function of fire. Some cases present with itching and pain like light pricks from needle tips, similar to flying sparks burning the skin. However, when sores and ulcers are frequently moxibusted or soaked in hot water, yet the itching intensifies, this is caused by mild heat assisting the pathogenic factor. In other cases, there is no itching because the heat relaxes the skin, opens the Couli (skin texture and pores), allows Yang Qi to dissipate, and facilitates the easy dispersion of heat, thus resulting in no itching. If cold water is poured on an itchy area, providing temporary relief followed by severe itching after some time, it is because coldness governs contraction, leading to the stagnation of Yang Qi which cannot disperse, while boiling heat arises internally, causing the itching to worsen again. When scratching relieves itching, it is because movement belongs to Yang, and Yang is associated with the transformation of Fire. Thus, gentle scratching can relieve itching due to the mild nature of Fire. Heavy scratching eliminates itching because the broken skin produces a pungent sensation, associated with the transformation of Metal. Pungency can disperse, so when the Metal transformation encounters the power of Fire, it resolves, and itching ceases. The *Neijing* states: Pain indicates Excess, while itching indicates Deficiency. Here, "Deficiency" does not refer to Cold-Deficiency, but rather signifies the degree of intensity of Heat-Fire. There are also cases of numbness in sores and ulcers where one feels neither pain nor itching. This is due to Qi deficiency failing to circulate, compounded by the obstruction of sore toxins and blockage of meridians, leading to numbness and loss of sensation, which varies in severity. "Ma" (numbness/tingling) is a lighter form of wood-like sensation, while "Mu" (woodiness/stiffness) is heavier. For example, sitting for a long time may cause legs and knees to feel stiff and numb; after stretching and waiting, circulation restores, indicating that "Ma" represents slight stagnation where Qi flows and Blood resumes circulation. Generally, before ulceration, numbness indicates the severity of toxin obstruction. After ulceration, numbness indicates muscle rot and depletion of Qi and Blood, reflecting the severity of Deficiency.

Zhang Jingyue stated: Regarding any carbuncle or toxic swelling with severe redness and pain, although internal treatment methods were previously outlined, decoctions act slowly. For urgent and unbearable pain, external applications are necessary. To achieve both pain relief and toxin resolution, nothing is more miraculous than Jiangyong San (Carbuncle-Reducing Powder). He also stated: Pain returning after pus discharge indicates Deficiency.

Li Dongyuan stated: The manifestations of sores and ulcers vary; Cold, Heat, Excess, and Deficiency can all cause pain. Methods for relieving pain are numerous. People generally believe that precious herbs like Ru Xiang (Olibanum) and Mo Yao (Myrrha) can stop pain, failing to realize that treatment must be adapted to the specific condition. For pain caused by Heat-Toxin, using cold-natured drugs to subdue the heat will naturally stop the pain. For pain caused by Cold-Evil, using warm-natured drugs to dispel the cold will naturally eliminate the pain. For pain due to Wind, remove the Wind; for pain due to Dampness, drain the Dampness; for pain due to Dryness, moisten it; for pain due to Obstruction, unblock it; for pain due to Deficiency, tonify it; for pain due to Excess, purge it; for pain due to pus retention, open it; for pain due to foul tissue erosion, guide it out; for disharmony of Yin and Yang, harmonize it; for blocked and stagnant meridians, promote flow. Adapting to changes according to circumstances makes one a superior physician; one must not rigidly adhere to formulas without flexibility. (From *Shi Shu*)

Gu Cheng stated: There are five types of pain in carbuncles and ulcers. At the initial stage, it is due to Qi stagnation and Blood coagulation, requiring methods to invigorate Blood and move Qi. When throbbing pain develops, it indicates muscle rot and pus formation, requiring internal support and pus drainage. If pain occurs before ulceration due to the mistaken application of cold medicines, aromatic drugs should be used for washing. If pain returns after ulceration and pus discharge, it is due to Deficiency, requiring tonification of Qi and Blood. If pain occurs after ulceration due to contact with foul odors, Ru Xiang (Olibanum) and Mo Yao (Myrrha) should be used to resolve it, and the pain will cease naturally.