What Are The Causes Of Sinusitis And How Is It Treated? Business by Steffy Alen - December 3, 2020December 3, 20202 Sinuses are small air pockets that are located behind your nose, cheekbones, forehead, and between the eyes. Sinuses can produce a thin and flowing liquid called mucous which protects the body by trapping and moving germs away. Sinusitis is an inflammation or swelling of the mucous tissue of the sinuses