The most common cause for acute sinusitis is a cold that does not get better in the usual 7 to 10 days that is normally takes a cold to go away. Swelling in the nasal passages and in the sinus drainage passages called ostium causes mucous to sit in small, closed spaces. Bacteria love to grow in this type of environment.
Untreated allergies can cause similar problems.
The symptoms may be very subtle, often missed by both the doctor and the patient. In chronic sinusitis, symptoms are present for more than 8-12 weeks. Patients with this condition require longer courses of antibiotics, often 4-6 weeks. They must be evaluated for possible underlying problems such as allergies, structural problems like enlarged adenoids or a deviated septum. Tests can also be done to make sure everything is functioning normally with their immune system.