A sinus infection, or sinusitis, occurs when the sinus cavities become inflamed due to an infection, allergies, or other underlying conditions. The sinuses are air-filled cavities in the skull and facial bones, which are responsible for filtering, humidifying, and warming the air we breathe. However, when they become blocked due to mucus buildup, bacteria, viruses, or fungi can thrive... https://venturaent.com/sinusitis-sinus-surgery/