7 months old baby runny nose is mostly caused by viral infection of the upper respiratory tract lesions, so that the nasal secretion increases and thus the phenomenon of runny, can be given antiviral drugs, such as ribavirin or interferon nasal spray, most of them need to be used in the onset of the disease within 1-3 days to be effective, if the use of antiviral drugs after 3 days is not very useful. Most viral infections are self-limiting, if there is only a simple runny nose with good mental status and normal appetite, there is no need for special medication, observation is sufficient, and most of them can be cured after 1 week. If there are symptoms of lower respiratory tract infection such as fever, increased respiratory rate and coughing, it is necessary to go to the hospital in time.