Sinus or Sinusitis also known as a sinus infection or rhinosinusitis, is inflammation of the sinuses resulting in symptoms. Common signs and symptoms include thick nasal mucus, a plugged nose, and pain in the face. Acute sinusitis can be triggered by a cold or allergies and may resolve on its own. Chronic sinusitis lasts up to eight weeks and may be caused by an infection or growths. Symptoms include headache, facial pain, runny nose, and nasal congestion.