Sinusitis is inflammation of the sinuses that occurs due to a viral, bacterial or fungal infectionThe sinuses are small, air-filled spaces inside the cheekbones and forehead, around the nose. They mucus produced by them drains into the nose through small channels: The frontal sinuses located in the area near the eyebrows, The maxillary sinuses located inside the cheekbones, The ethmoid sinuses between the eyes and,