It may or may not be normal for a 1-month-old infant to sleep with his mouth open. Clinically, the following analysis: 1, the normal situation, mainly infants sleep in the wrong position, such as the pillow may be high or sleep too much head back will lead to open mouth breathing, then adjust the sleep position, the child may not open his mouth when sleeping. 2, the child has been open mouth breathing when sleeping, through changing the position and other methods did not improve, obviously feel nasal ventilation is not good, it may be due to cold, cold It may also be due to the dryness of the patient’s nasal cavity, which induces blockage of the nasal cavity with nasal stool, or the blockage of the nose induced by the return of milk. Generally, you can find a doctor to check the nasal cavity to see which one it is, and then give treatment so that the nasal congestion can be relieved and the open mouth breathing can be relieved.