There are several reasons why it is easy to cough at night, as follows: first, if there is a lesion in the lungs that needs to be drained, and the body is in an upright position when awake during the day, these inflammatory secretions are deposited in the lungs, and it is difficult to go up to the top of the lungs to drain them. Because it is a process from bottom to top to discharge phlegm from the lungs, it is very troublesome like going upstairs, but lying down becomes horizontal, sometimes when there is phlegm deposited in the lungs, because the upright state is not good to discharge phlegm, it is necessary to lie down or lie down to find a suitable position for drainage. At night when sleeping is exactly lying down, if there is phlegm in the lungs is easy to come out, will cause cough. Second, the bed linen has a lot of dust mites and fiber debris hidden inside, some people have allergic diseases, when lying down, because the airflow inside the linen is pressed out by the body, with debris diffused in the air of the lying down body space, after inhalation can trigger respiratory sensitivity, triggering a cough. At this time, we should pay attention to drying the bedding, washing the pillows, and reducing the number of dust mites, which are less likely to cause coughing when the amount is small. Thirdly, when you are sleeping, your breathing is very deep and large as you enter the sleep state. This time so much airflow in the airway back and forth, if the sleep room air is too dry, often triggering airway discomfort. If the taste of dinner is particularly heavy, it happens to echo the dryness of the outside air, which also tends to trigger airway irritation and coughing.