Sinusitis is an inflammation (swelling) of the mucous membranes that line the sinus cavities. This is not the same as a sinus infection. The inflammation of the mucous membranes that line the sinus cavities can interfere with normal sinus drainage and cause increased mucus production. Untreated and prolonged sinus inflammation can lead to a sinus infection and increased symptoms. To understand sinusitis, it is critical to also understand the sinuses themselves.
Health experts estimate that 37 million Americans are affected by sinusitis every year-and spend nearly $6 billion annually on the costs of battling it. Sinusitis is usually more uncomfortable than dangerous, but in very rare cases, infection can spread from the sinuses to the bones or even the brain.
Acute sinusitis often goes away in a few weeks, either on its own or after treatment with washing out the nose with salt water, decongestants or antibiotics. If sinusitis lasts less than four weeks, it is considered acute sinusitis. However, for many people, sinusitis is a chronic problem. For these people, longer-term medicines or even surgery may be necessary.
The sinuses are a part of the upper respiratory system. Adults and older children have four groups of sinus cavities (maxillary, ethmoid, frontal and sphenoid) located within the bones surrounding the nose. Very young children have small sinus passages and cavities rather than fully formed sinuses. Under normal daily conditions, the sinuses produce up to 1.5 liters of mucus per day. Allergy, infection or environmental triggers may increase mucus production or change the characteristics of the mucus in the nose and cause symptoms. Each sinus cavity has an opening into the nose to allow for drainage of this mucus. Therefore, anything that causes swelling in the nose may lead to obstruction or blockage of the sinuses leading to infection and more sinus problems. To work properly, the sinuses need adequate mucus drainage and a functioning immune system to fight off infections and inflammation.