What causes a sinus headache?
While a sinus inflammation (sinusitis) may be caused by a viral infection and causes swelling in the nose (inflammation). This inflammation and decreased ability of the sinuses to drain also may be caused by an allergic reaction such as hay fever. The inflammation causes swelling and increased fluid production. In the sinuses, this decreases the ability of the sinuses to drain. This increased inflammatory fluid production and the decrease in drainage causes the pain and pressure of a sinus headache.
After a period of time bacteria and viruses may travel from the nasal cavities into the stagnant fluid within the sinus cavity and cause an infection. Most sinus infections are due to viruses. Viruses are the more likely cause if symptoms have been present for less than a week and are not getting worse. Bacterial infections typically will follow the initial period of inflammation from a viral infection or other significant sinus blockage. Less commonly, fungal infections may cause a sinus infection, and even more rarely, tumors can invade the sinus.
The maxillary sinus sits underneath the eye within the cheekbone. The upper teeth attach to the lower portion of this bone, and dental infections can travel up the root of the tooth and infect the sinus directly.
Because there is almost always nasal inflammation associated with sinus inflammation, the illness is now often referred to as rhinosinusitis.