Sinusitis

Sinus infections happen when fluid builds up in the air-filled pockets in the face (sinuses). This fluid buildup allows germs to grow. Viruses cause most sinus infections, but bacteria can cause some sinus infections. Sinusitis is an inflammation of the sinuses that can cause them to get blocked and filled with fluid. It is usually caused by colds or allergies. An infection could result from the blockage. The sinuses are four paired cavities (spaces) in the head. They are connected by narrow channels. The sinuses make thin mucus that drains out of the channels of the nose. This drainage helps keep the nose clean and free of bacteria.