Dear Doctors: Can you please talk about sinusitis? I’ve been having headaches and postnasal drip for a few months, and I thought it was because of my allergies. But my brother, who is a nurse, thinks it could be sinusitis. What are the symptoms, and how is it treated?

Dear Reader: Sinusitis occurs when inflammation or infection cause swelling in the tissues that line the paranasal sinuses. Often referred to simply as sinuses, these are two pairs of air-filled cavities that are connected by narrow passageways.