Briefer bouts of the condition, called acute sinusitis, are even more common. Sinuses are the hollow air spaces in the front of the skull. Because they open into the nose and share a continuous membrane with it, anything that stuffs up the nose can cause the sinus membrane to swell. That can block the sinus openings and prevent mucus from draining out. The trapped mucus then becomes a breeding ground for bacterial infection, which causes or complicates most cases of sinusitis.
Problem is, the condition is often overlooked or mistreated.
Distinguishing among colds, allergies and sinusitis can be tricky. They can all cause some of the same symptoms, such as congestion and coughing. Further, an allergy often coexists with sinusitis, and a cold can overlap or precede it, too. But certain symptoms, while not exclusive to sinusitis, strongly suggest it, particularly if they persist. Dry heat lowers the humidity, inhibits mucus secretion and is a major contributor to sinusitis.