Infants who are not breathing well and have phlegm in their nasal passages should consider sinusitis, allergic rhinitis and hypertrophic rhinitis as possible causes. 1. Sinusitis: Repeated respiratory infections in infants can easily lead to sinusitis. Most acute episodes of sinusitis can be characterized by fever, nasal congestion, nasal discharge, headache and decreased sense of smell. 2. Allergic rhinitis: manifested as nasal congestion, sneezing, runny nose, itchy nose and other symptoms. Some infants have obvious seasonal correlation. 3. Hypertrophic rhinitis: It can also manifest as nasal congestion, runny nose, sneezing, which may be accompanied by more purulent secretion. There may be decreased sense of smell, foreign body sensation and itchiness in the nose. Some infants may have tinnitus, ear congestion, and recurrent pharyngitis at the same time. There are other reasons for babies to have phlegm sounds inside the nasal cavity when they are not breathing well, so it is recommended to seek medical attention in time to find out the cause and cooperate with the doctor for treatment.