Sinusitis can occur if there is interference from the air flows from and into the sinus cavity and the existence of interference of mucous expel. The presence of fever, flu, allergic and irritant materials can cause swelling on Ostia, so that this drainage holes become clogged and disrupt the sinus air flows and mucus expel. Another cause of Ostia clogging is tumors and trauma. Mucous fluid drainage that got out from the sinus cavity can also be obstructed by the coagulation of mucous liquid itself. This coagulation is occurs due to giving of antihistamine drug, cystic fibro disease and others.

The cells that produced mucous have a fine hair (cilia) which is always moves to push the mucous fluid out of the sinus cavity. Cigarette smoke is the trigger of the destruction of this fine hair so that the mucous expel becomes disrupted. Mucous fluid that accumulated in the sinus cavity for a long time then becomes a good place for the lives of bacteria, viruses and fungi.

Sinusitis can be divided into two major types which are based on the period of illness (acute, sub acute, chronic) and based on the type of inflammation that occurs (infection and non-infectious). It can be called acute sinusitis when the duration of illness is less than 30 days. Sub acute sinusitis when the disease is lasted for 1 month to 3 months, while chronic sinusitis when the disease is suffers more than 3 months.

Sinusitis infection usually is caused by a virus although on some cases are caused by bacteria. While non-infectious sinusitis mostly caused by allergies and irritation of material substances. Sub acute and chronic sinusitis is often a continuation of acute sinusitis which do not getting an adequate treatment.