Changes in temperature or air pressure of anything that causes swelling in your sinuses or keeps the cilia from sweeping the mucus out of the sinuses can cause sinusitis.
Sinusitis can be caused by allergies. Using too much decongestant nasal sprays, smoking, swimming or diving can also increase the risk of sinusitis.
Some patients have growths called nasal polyps that block their sinus passages and cause sinusitis.
When sinusitis is caused by a bacterial or viral infection, the patient suffers from a sinus infection. Sinus infection may occur after one has a cold. The cold virus attacks the lining of the sinuses which cause them to swell and become narrow. The body will respond to the virus by producing more mucus which gets blocked up in the swollen sinuses. This built-up of mucus creates an environment for bacteria to grow. The bacteria can cause a sinus infection.