The sinuses are a series of small air cavities in the skull, located within the cheek bones, behind the nose and in the forehead. They are connected to the throat and nasal passages and represent the uppermost components of the respiratory tract.Sometimes, these cavities can become inflamed and filled with mucus and cause sinus congestion. There are many different things which can cause this to happen, and the medicinal treatments will vary depending on the specific cause. Some of the most common diseases and environmental factors which can cause sinus congestion include: Allergens and dust particles The common cold , Flu, Nasal polyps, Deviated septum , Sinusitis.You should also see a doctor if you experience the following symptoms along with sinus congestion, pressure, or irritation: changes in vision, fever of 102°F (38.9°C) or higher, increased greenish or bloody nasal discharge, mucus with a strong odor, wheezing