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Sinusitis (Sinus Infection)

Sinusitis is an inflammation of the membranes lining the paranasal sinuses—small air-filled spaces located within the skull or bones of the head surrounding the nose. Sinusitis can be caused by an infection or other health problem, and symptoms include facial pain and nasal discharge. Nearly 30 million adults in the United States are diagnosed with sinusitis each year, according to the Centers for Disease Control and Prevention.

The paranasal sinuses comprise four pairs of air-filled spaces:

  1. Frontal sinuses—over the eyes in the brow area
  2. Ethmoid sinuses—just behind the bridge of the nose, between the eyes
  3. Maxillary sinuses—inside each cheekbone
  4. Sphenoid sinuses—behind the ethmoids in the upper region of the nose and behind the eyes

There are two basic types of sinusitis:

  1. Acute, which lasts up to 4 weeks
  2. Chronic, which lasts more than 12 weeks and can continue for months or years

NIAID supports research to better understand the causes of sinusitis and to develop new treatments for the condition.

Diagram of the face, showing frontal, ethmoid, maxillary, and sphenoid sinuses
Credit: NIAID

Last Updated May 15, 2015

Last Reviewed May 15, 2015