Internal heat and external heat can be judged mainly from the cause and symptoms. Internal heat is relative to external fever, which refers to the heat of yin and yang in the internal organs, while external heat refers to the heat of the skin and muscle surface. 1. Internal heat: internal heat is divided into real and imaginary, real heat to the heart, liver, lungs, stomach real heat is common, the patient may appear high fever, face red, yellow and red urine, constipation, etc.; imaginary fire is often seen in the internal injuries and labor, the patient may appear hot flashes (a burst of fever), night sweats (abnormal sweating after going to sleep, waking up sweating stops), emaciation and so on. 2. External heat: Pi generally refers to the manifestation of external heat, which may appear as body heat, red face, thirst for hot drinks, body heat and cover, cold extremities (cold extremities, even cold to the elbows and above the knees), dysentery clearing the grain, urine clear and long and other symptoms. If the above symptoms occur, consult a doctor promptly, who will give targeted treatment after clarifying the cause of the disease.