The reasons for coughing up phlegm and itching throat at night include nasal diseases, throat diseases, allergies and so on. 1. Nasal diseases: Nasal diseases are common such as allergic rhinitis, chronic rhinitis, sinusitis, etc., can appear post-nasal drip syndrome, in the night time when the nose backflow leads to itchy throat, cough with phlegm and other symptoms. 2. Diseases of the throat: such as chronic pharyngitis, reflux pharyngitis, tonsillitis and other inflammation of the throat itself, the symptoms can occur. Possible triggers include viral or bacterial infections, inappropriate use of voice, gastroesophageal reflux and so on. 3. Allergy: After contact with allergens, the mucous membrane of the throat can undergo metamorphic reactions, with an increase in immune cells and the release of inflammatory mediators, leading to chronic inflammation of the throat. In serious cases, it is recommended to consult a doctor in time to check the reasons for coughing up phlegm at night and itchy throat, and actively cooperate with the doctor to treat the disease according to the individual’s situation.