Taiyang disease (Disease of the Taiyang channel) presents with heat in the chest, pathogenic factors (here referring to cold evil) in the stomach, abdominal pain, and a desire to vomit; Huanglian Tang (Coptis Decoction) is the primary treatment.

This heat does not manifest on the exterior but resides in the chest; it is heat accumulated prior to contracting the cold damage. The "pathogenic factor" refers to cold evil. Yang Qi receives its qi in the chest; if there is heat in the chest, it manifests upward on the head and face. Therefore, cold evil enters the stomach from the hypochondrium. This corresponds to what *Neijing* (The Inner Canon) states: "If struck at the hypochondrium, it descends into Shaoyang." Currently, cold evil in the stomach creates an obstruction, preventing the heat in the chest from descending, causing it to flare upward and induce vomiting; the Yang Qi of the epigastrium cannot disperse outward, resulting in abdominal pain. Since the heat is not on the exterior, there is no fever; since the cold is not on the exterior, there is no aversion to cold. The chest is considered the "exterior of the interior," and the abdomen is the "interior of the interior." This disease occurs in the semi-exterior-semi-interior aspect of the Fu organs (Six Bowels), not in the semi-exterior-semi-interior aspect of the physical body. Alternating chills and fever occur when pathogens enter the channels from the cheek area, affecting the semi-exterior-semi-interior aspect of the form and body. For instance, after five or six days, if one experiences fullness and distress in the chest and hypochondrium, irritability, and frequent desire to vomit, this indicates that cold damage has transmitted and transformed into heat, rather than pre-existing heat. If abdominal pain occurs, it signifies cold evil moving from the chest to the abdomen, which differs from the case where evil moves from the hypochondrium to the chest and stomach. Therefore, Huanglian (Rhizoma Coptidis) is used as the sovereign herb, also to supplement the insufficiency of Chaihu Tang (Bupleurum Decoction).

A desire to vomit without actual vomiting, and abdominal pain without diarrhea, resembles conditions modernly referred to as Gan Huoluan (Dry Cholera) or Jiaochangsha (Intestinal Colic).

Huanglian Tang Prescription:
Huanglian (Rhizoma Coptidis) [3 liang], Ganjiang (Radix Zingiberis Recens) [3 liang], Zhigancao (Radix Glycyrrhizae Preparata) [2 liang], Guizhi (Ramulus Cinnamomi) [3 liang], Renshen (Radix Ginseng) [2 liang], Banxia (Rhizoma Pinelliae Preparata) [0.5 sheng], Dazao (Fructus Jujubae) [12 pieces, split].
Boil in 10 dou of water until reduced to 6 sheng. Remove the dregs. Take 1 sheng warm, three times during the day and twice at night.

This is also a modified formula derived from Chaihu Tang. Since there is no heat on the exterior and abdominal pain is present, Chaihu (Radix Bupleuri) and Huangqin (Radix Scutellariae) are omitted. Huanglian serves as the sovereign herb to drain accumulated heat in the chest; Ganjiang and Guizhi drive out cold evil in the stomach; Gancao and Dazao act as assistant herbs to alleviate abdominal pain; Banxia eliminates vomiting; and Renshen tonifies deficiency. Although there is no alternating chills and fever on the exterior, there is a standoff between cold and heat within the interior, thus still adhering to the therapeutic principles for Shaoyang disease (Disease of the Shaoyang channel).

This formula is largely similar to Xiexin Tang (Gallbladder-Draining Decoction variants), but is not named Xiexin Tang because the heat in the chest is pre-existing, rather than being a result of cold and heat knotting together at the Xin Xia (subcostal/epigastric region). The substitution of sovereign and minister herbs demonstrates precise clinical judgment.