A sinus infection, also called acute sinusitis, develops when your sinuses become inflamed and swollen. As a result, mucus becomes trapped in the sinuses, which leads to an infection. Acute sinus infections appear suddenly, then get better within four weeks.
In most cases, acute sinusitis is caused by the same virus that’s responsible for the common cold. You may be at a higher risk for getting sinus infections if you have hay fever or other allergies that affect your sinuses.
Patients with a deviated nasal septum or nasal polyps are also more susceptible to sinus infections.