1. Causes of cold and runny nose in babies. Cold and runny nose in babies are caused by viruses. Common viruses include rhinovirus, adenovirus, parainfluenza virus, etc. These viruses will invade the baby\’s respiratory tract, causing congestion of the nasal mucosa, increased secretions, and symptoms such as sneezing and sore throat. 2. How to prevent your baby from getting a cold and runny nose 1. Maintain good hygiene habits: Let your children develop a good habit of washing hands frequently and avoid contact with people with infectious diseases. 2. Keep warm: In cold weather, put on appropriate clothes for your children to avoid catching cold.