Alternating chills and fever (alternating episodes of cold and heat) arise from the mutual excess of Yin and Yang, and the struggle between pathogenic factors and healthy Qi. Generally, when Yang is insufficient, Yin pathogens emerge from the exterior and contend with healthy Qi, causing Yin to prevail and manifest as chills; when Yin is insufficient, Yang pathogens enter the interior and contend with healthy Qi, causing Yang to prevail and manifest as fever. When pathogens reside more in the exterior, chills predominate; when they reside more in the interior, fever predominates; when they reside in the half-exterior half-interior region, chills and fever are equal, appearing intermittently as they come and go. Xiao Chai Hu Tang (Minor Bupleurum Decoction) specifically treats alternating chills and fever. If chills predominate, add Guizhi (Cinnamon Twig); if fever predominates, add Dahuang (Rhubarb Root). This is the fundamental principle. There are cases where extreme heat paradoxically presents with aversion to cold; in summer months, Guizhi should not be used. There are also cases in women where heat entering the Blood Chamber (uterus and Chong and Ren vessels) causes alternating chills and fever; these also belong to the Shaoyang channel disease.

[Harmonizing Method] For diseases in the half-exterior half-interior presenting with alternating chills and fever, use Xiao Chai Hu Tang. If fever predominates, use Baihu Jia Guizhi Tang (White Tiger plus Cinnamon Twig Decoction). If chills predominate, use Chaihu Jianggui Tang (Bupleurum, Ginger, and Cinnamon Twig Decoction). Fever followed by chills indicates Yin insufficiency; use Xiao Chai Hu Shaoyao Tang (Minor Bupleurum plus Peony Decoction). Restlessness, frequent vomiting, hypochondriac fullness, and loss of appetite indicate Xiao Chai Hu Tang. Chest fullness, or diarrhea accompanied by cough, indicate removing Zao (Jujube Fruit) and adding Wuweizi (Schisandra Berry) from Xiao Chai Hu Tang. Thirst without vomiting, sweating on the head, difficulty in urination, and chest fullness indicate Chaihu Ganjiang Tang (Bupleurum and Dried Ginger Decoction). No vomiting, clear stools, and alternating chills and fever occurring two or three times a day indicate Guizhi Mahuang Banban Tang (Equal Parts of Cinnamon Twig and Ephedra Decoction). In Jueyin disease, if aversion to cold and fever resemble malaria, it indicates the disease is about to resolve; use Guizhi Mahuang Banban Tang. Taiyang syndrome resembling malaria, occurring twice a day with a surging pulse, indicates Guizhi Er Mahuang Yi Tang (Two Parts Cinnamon Twig and One Part Ephedra Decoction). In women, after wind-stroke, continuous alternating chills and fever with timed fever and sudden cessation of menstruation indicates heat entering the Blood Chamber, where blood must be stagnant, causing symptoms like malaria; use Xiao Chai Hu Tang.

[Yuespi Method] Aversion to cold with fever and a faint pulse indicate that diaphoresis should not be performed further; use Guizhi Er Yuespi Yi Tang (Two Parts Cinnamon Twig and One Part Yuespi Decoction).

[Double-Resolving Method] After ten-plus days of illness, with heat binding in the interior and recurring alternating chills and fever, use Da Chai Hu Tang (Major Bupleurum Decoction).

[Purgative Method] Alternating chills and fever with aversion to heat indicates stomach excess (stomach fu-organ excess); use Tiaowei Chengqi Tang (Regulating the Stomach and Guiding Out Decoction).

In Zhang Zhongjing's writings, there are only clauses regarding "more heat and less cold," but no syndromes of "more cold and less heat."

A floating and moderate pulse with cold extremities indicates Mahuang Guizhi Banban Tang (Equal Parts of Ephedra and Cinnamon Twig Decoction).