ear, nose, and throat disorders
Sinusitis
Acute sinusitis
Sinusitis is defined as acute if it is totally resolved in less than 30 days. In people who have a normally functioning Overview of the Immune System , acute sinusitis is usually caused by a viral infection. Sometimes acute sinusitis is caused by bacteria. Infection often develops after something blocks the openings to the sinuses. Such blockage commonly results from a viral infection of the upper airways, such as the Common Cold . During a cold, the swollen mucous membranes of the nasal cavity tend to block the openings of the sinuses. Air in the sinuses is absorbed into the bloodstream, and the pressure inside the sinuses decreases, causing pain and drawing fluid into the sinuses. This fluid is a breeding ground for bacteria. White blood cells and more fluid enter the sinuses to fight the bacteria. This influx increases the pressure and causes more pain. Seasonal Allergies also cause mucous membrane swelling, which blocks the openings to the sinuses. Additionally, people with a deviated septum are more prone to blocked sinuses. The sinuses are hollow cavities in the bones around the nose. The two frontal sinuses are located just above the eyebrows. The two maxillary sinuses are located in the cheekbones. The two groups of ethmoid sinuses are located on either side of the nasal cavity. The two sphenoid sinuses (not shown) are located behind the ethmoid sinuses. 