In general, all animals in the natural world, except for cold-blooded ones, have a fire of life burning within them. Without this fire, life would cease.
In the human body, this fire is normally maintained at a constant temperature. If this fire becomes too intense, it is considered abnormal "pathogenic fire".
According to the location where pathogenic fire appears, Traditional Chinese Medicine classifies it into three types. The first is called "Upper Jiao Fire," which broadly refers to heat-related symptoms in the upper part of the body, such as dizziness and a sore throat. The second is called "Middle Jiao Fire," such as gastric discomfort and vexing heat with thirst caused by organ diseases. The third is called "Lower Jiao Fire," a general term for pathogenic fire in the lower parts of the body, such as constipation and dark urine.
However, some TCM practitioners believe this three-type classification is too general. Instead, they classify "pathogenic fire" based on the orifices of the organs, dividing it into Heart Fire, Liver Fire, Lung Fire, Stomach Fire, and Kidney Fire. Heart Fire can be of two types: deficiency and excess. Deficiency fire is characterized by low-grade fever, night sweats, vexation, and a dry mouth. Excess fire is characterized by recurrent mouth ulcers, a dry mouth, scanty and dark urine, and irritability.
The main cause of Liver Fire is emotional distress. A common characteristic of Liver Fire is an inability to control one's temper and a constant feeling of anger. Studies have shown that women are more prone to "fire" than men, especially elderly women, and the duration of the condition is longer for them. Wheezing and shortness of breath are called "Lung Fire," characterized by a dry cough with little or no phlegm, tidal fever, night sweats, heat in the palms and soles, insomnia, and a red tongue.
Patients with Stomach Fire generally have a bad taste in the mouth, in addition to dry stools, a bitter taste in the mouth, and hiccups. Kidney Fire manifests as dizziness, blurred vision, tinnitus, deafness, soreness and weakness of the lower back, tidal fever, night sweats, and vexation with heat in the five centers (palms, soles, chest, and epigastrium).