Definition of Sinusitis:

Sinusitis refers to inflammation of the sinuses that occurs with a viral, bacterial, or fungal infection.

See also: Chronic sinusitis

Causes, incidence, and risk factors:

The sinuses are air-filled spaces in the skull (behind the forehead, nasal bones, cheeks, and eyes) that are lined with mucus membranes. Healthy sinuses contain no bacteria or other germs. Usually, mucus is able to drain out and air is able to circulate.

When the sinus openings become blocked or too much mucus builds up, bacteria and other germs can grow more easily.

Sinusitis can occur from one of these conditions:

• Small hairs (cilia) in the sinuses, which help move mucus out, do not work properly due to some medical conditions.
• Colds and allergies may cause too much mucus to be made or block the opening of the sinuses.
• A deviated nasal septum, nasal bone spur, or nasal polyps may block the opening of the sinuses.

Sinusitis can be:

• Acute -- symptoms last up to 4 weeks
• Sub-acute -- symptoms last 4 - 12 weeks
• Chronic -- symptoms last 3 months or longer

Acute sinusitis is usually caused by a bacterial infection in the sinuses that results from an upper respiratory tract infection. Chronic sinusitis refers to long-term swelling and inflammation of the sinuses that may be caused by bacteria or a fungus.

The following may increase your risk or your child's risk of developing sinusitis:

• Allergic rhinitis or hay fever
• Cystic fibrosis
• Day care
• Diseases that prevent the cilia from working properly, such as Kartagener syndrome and immotile cilia syndrome.
• Changes in altitude (flying or scuba diving)
• Large adenoids
• Smoking
• Tooth infections (rare)
• Weakened immune system from HIV or chemotherapy