Sinusitis is inflammation of the sinuses caused by infection, allergies, or blockages. Acute sinusitis lasts less than 4 weeks while chronic sinusitis persists over 12 weeks. Symptoms include nasal congestion, headache, facial pain, and reduced sense of smell. Diagnosis involves physical exam, x-rays, or CT scan. Treatment depends on cause but may include saline rinses, decongestants, antibiotics, steroids, or surgery to improve drainage if drug therapy is ineffective. Complications can include bone infections, eye or brain infections if not properly treated.