Infants from clear water-like nasal mucus into yellow pus-like nasal mucus may be acute upper respiratory tract infection; may also be allergic rhinitis secondary bacterial infection; more general treatment and drug therapy. 1. Acute upper respiratory tract infection: it is an acute infection of the upper respiratory tract caused by a variety of pathogens, commonly known as “colds”, and it is the most common disease among children. More than 90% of viral infections, viral infections secondary to bacterial infections can appear clear watery nasal mucus into yellow pus-like nasal mucus. Parents should pay attention to the ventilation of the room and encourage children to drink more water. There is no specific drug for viral infections; for secondary bacterial infections, antibiotics such as cefixime are often used. 2. Allergic rhinitis secondary to bacterial infection: the above situation can also occur, then you need to stay away from the suspected allergens, for bacterial infection can be treated with antibiotics. All of the above drugs should be used under the guidance of a doctor, avoid self-medication. When infants have runny nose, it is recommended to consult the doctor in time, complete the relevant examination and then be targeted treatment; when the clear nasal mucus turns into yellow nasal mucus, it suggests that the condition is aggravated, and may be secondary to bacterial infections, so it is necessary to comply with the doctor’s instructions to take medication.