Hello. Thanks for asking on Healthcaremagic. Mucus is normally secreted in nasal and throat glands important for moistening and protective response. Excessive mucus might lead to post nasal drip. Causes are colds, flu, allergies, sinusitis, deviated nasal septum, dry air etc. It is important to identify the cause. Sinus infection and allergies are a major cause. In case he has associated pain over the sinus area on face it would most probably be sinusitis. If it exacerbates during a specific season allergy might be causing it. Treatments might include antibiotics for sinusitis, and antihistamines and mast cell stabilizers for both. Steam inhalation is very helpful. You can start steam right away and Medicate him after consulting an ent specialist. Hope I helped. Thanks.