How long does it take a sinus infection to clear up?

Depends: An acute sinus infection can last 2-4 weeks because antibiotics have a difficult time penetrating into the sinuses and clearing up the infection. If there are structural problems with draining the sinus, it can be even longer or become a chronic infection.

Sinus infection: It depends on the cause of the infection - bacterial vs viral. Most of the sinus infections we get are actually caused by a virus and will clear up by themselves within 2 weeks. If at that time, there are still symptoms, we consider a bacterial source and may use antibiotics.