If you do not have a cold, but one of your noses is not ventilated, you should first rule out allergies, because allergies can easily lead to nasal congestion and edema, which can also lead to nasal hypoventilation. If allergies do occur, you need to go to the hospital to check the allergens and then check the blood routine, because when allergies occur, there is usually an increase in eosinophils in the blood routine, then you can use anti-allergy drugs to relieve, for example, adults can use loratadine, and infants can use desloratadine to treat. If allergies are not present, it is likely that the nasal cavity is not ventilated due to a nasal lesion, so the first step is to go to the ENT and have the nasal cavity examined by a rhinoscope. If there is turbinate hypertrophy or rhinitis, the nose may be blocked and anti-inflammatory treatment is needed. If the turbinate hypertrophy is more serious, timely surgery is also needed.