Conditions InDepth: Sinusitis

Sinusitis is inflammation and infection of the sinus cavities. The sinus cavities are air-filled spaces in the skull. Sinusitis usually occurs with rhinitis. Rhinitis is inflammation in the nasal passages. When sinusitis and rhinitis happen together, it is called rhinosinusitis. Rhinosinusitis may be:

  • Acute—lasts less than 4 weeks
  • Subacute —lasts 4 to 12 weeks
  • Recurrent —4 or more episodes per year with no symptoms between episodes
  • Chronic —lasts more than 12 weeks

Paranasal Sinuses

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Acute sinusitis is linked to certain bacteria, viruses, and other causes.

The bacteria are often found in the nose and throat of healthy people. They cause other common conditions. Examples are acute bronchitis and ear infections.

The common cold or other upper respiratory infection often happens just before a bacterial infection.

Certain other bacteria and fungi can cause chronic sinusitis.

Sinus Infection

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Sinusitis starts with swelling of the nasal and sinus passages. Tiny hairs called cilia usually help shift mucus out of the sinuses. With sinusitis, these hairs stop working as well as they should. The swelling and impaired cilia make it hard for mucus to move out of the sinuses. Mucus buildup and air lead to pressure and pain. It also creates a place for bacteria and viruses to grow.

Sinusitis is a very common problem.



Acute rhinosinusitis in adults. EBSCO DynaMed website. Available at: Accessed November 15, 2021.
Chronic rhinosinusitis. EBSCO DynaMed website. Available at: Accessed November 15, 2021.
Sinusitis. American Academy of Otolaryngology—Head and Neck Surgery website. Available at: Accessed November 15, 2021.
Sinusitis overview. American Academy of Allergy, Asthma & Immunology website. Available at: Accessed November 15, 2021.
Last reviewed November 2021 by EBSCO Medical Review Board David L. Horn, MD, FACP
Last Updated: 11/17/2021

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