Sinusitis means your sinuses are infected or inflamed. Your sinuses are hollow air spaces within the bones surrounding the nose. They produce mucus, which drains into the nose. If your nose is swollen, this can block the sinuses and cause pain and infection.
Sinusitis can be acute, lasting for less than four weeks, or chronic, lasting much longer. Acute sinusitis often starts as a cold, which then turns into a bacterial infection. Allergies, pollutants, nasal problems and certain diseases can also cause sinusitis.
Symptoms of sinusitis can include fever, weakness, fatigue, cough and congestion. There may also be mucus drainage in the back of the throat, called postnasal drip. Treatments include antibiotics, decongestants and pain relievers. Using heat pads on the inflamed area, saline nasal sprays and vaporizers can also help.
NIH: National Institute of Allergy and Infectious Diseases