most often the result of a
viral infectionthat causes the
mucous membranelining the inside of the nose and the
sinuses to become
The mucous membrane swells when it becomes
inflamed, blocking the drainage of fluid from the sinuses into the nose and
Mucus and fluid build up inside the
sinuses, causing pressure and pain.
Bacteria are more likely to
grow in sinuses that are unable to drain properly.
Bacterial infectionin the sinuses often causes more
inflammation and pain.
Colds usually trigger this process, but any factor that
causes the mucous membrane to become inflamed may lead to sinusitis. Many
people with nasal allergies (allergic rhinitis), for instance, are
likely to have recurring or long-term (chronic) sinus infections. Nasal
polyps, foreign objects (usually in children),
structural problems in the nose such as a
deviated septum, and other conditions can also block
the nasal passages, increasing the risk of sinusitis.