The child’s physical fitness is relatively poor, it is easy to be infected by the outside world, and the runny nose is a common physiological phenomenon in children, causing the baby to run a clear nose for a number of reasons, which can be categorized into the following situations: First, the stimulation of cold air. The baby’s nasal mucosa is relatively fragile, if the outside cold air is too dry, the baby inhaled into the nasal cavity will cause the nasal cavity to be stimulated, thus producing mucus, which is snot. This situation generally does not need treatment, only need to give the child to do enough warm work can be. Second, the early stage of cold. Babies in the growth and development stage, it is easy to be infected by external bacteria, if once a cold occurs, it is very likely to produce the phenomenon of runny nose, so daily pay attention to the child’s physical health, avoid colds. Third, external environmental stimulation. Some families have excessive formaldehyde, or buy furniture with pungent wood flavor, although it is insignificant for adults, but small children’s nasal mucosa are more fragile, if excessive inhalation of such gases, it will also cause stimulation of the nasal cavity, resulting in an increase in nasal discharge. The runny nose in this case is usually accompanied by sneezing and nose itching. Finally, the baby’s nose is very fragile during growth and development, so parents must pay attention to the child’s daily habits when bringing up the child, to minimize environmental stimulation of the nasal mucosa.