The sinuses are cavities in your skull located around the eyes and behind the nose. Sinus pockets are also referred to as paranasal sinuses. These cavities lighten the weight of the skull. They also filter and moisten the air you breathe and give resonance to your voice. The sinuses are lined with very fine hair-like cells called cilia. The cilia help drain mucus through the sinus passages into the nose.
Rhinosinusitis, commonly referred to as sinusitis, occurs when the sinus openings become blocked or too much mucus builds up causing one or more of the cavities to become inflamed or swollen. Allergic rhinitis or asthma can be associated with chronic sinusitis.