Azithromycin for Sinus Infections: Uses, Effectiveness, and Buying Guide Every year, millions of people experience sinus infections, often known as sinusitis. They are caused by bacteria, viruses, or even allergies, and they cause inflammation of the sinuses, resulting in symptoms including congestion, headaches, facial pain, and thick nasal discharge. When treating bacterial sinus infections, antibiotics like azithromycin are commonly used to help remove the...