Cold and heat are two aspects of the nature of the disease. Cold and heat reflect the prevalence and decline of yin and yang in the body, which can be judged simply from the symptoms, but also in combination with the tongue and pulse. Cold cough is usually caused by external wind and cold, or a prolonged cough that is not treated in time, and is accompanied by coldness and warmth, a shaky white face, cold and weak limbs, a light mouth and no thirst, clear and thin sputum, clear and long urine or thin stool, a light white or moist tongue coating, and a slow or normal heart rate. Heat cough is usually caused by external wind-heat, cold that is not treated in time and turns into heat in the lungs, the seven emotions that are too extreme and turn into heat, or a poor diet that generates dampness and heat inside and fumigates the lung yin. The symptoms of heat cough include fear of heat and cold, thirst for cold drinks, redness of the face and eyes, restlessness, yellow and thick sputum, short and red urine, dry stools, red tongue with yellow coating and dryness, and fast heart rate.