The sinuses are a system of interconnecting hollow cavities in the skull. Mucosa, the lining of the sinuses, can get inflamed. This can result in an obstruction to the sinus pathways, which often causes the condition known as sinusitis.
There are some factors that can lead to the inflammation of the mucosa (sinusitis) such as allergies, reflux disease, deviated septum, a common cold, nasal polyps, and other chronic diseases. The causes are varied, but most are treated through medication and avoidance of the triggering situations.
Symptoms of a sinus infection include: discolored nasal drainage, nasal congestion, mouth breathing, lethargy/lack of energy, headaches, inability to breathe through one or both sides of your nose, facial pain, sore upper teeth.