Acute rhinosinusitis occurs when the lining of the inside of the nose and the sinuses become irritated and swollen. It is also called sinusitis.
Sinuses are air-filled spaces in the skull behind the face. They help to filter out pollutants, microorganisms, dust, and other irritants. Adults have four paired sinus cavities. They are kept moist and clean by a lining of mucosa. Things such as pollen, smoke, and chemical fumes can irritate the mucosa. It can then swell up. As a response to irritation, the mucosa makes more mucus and other fluids. Tiny, hairlike cilia cover the mucosa. Cilia help carry mucus toward the opening of the sinus. Too much mucus may cause the cilia to stop working. This blocks the sinus opening. A buildup of fluid in the sinuses then causes pain and pressure.
Bacteria can become trapped in this fluid leading to an infection.