Sinusitis is an inflammation (swelling) of the mucous membranes that line the sinus cavities. This can interfere with normal sinus drainage and cause increased mucus production. Untreated and prolonged sinus inflammation can lead to infection and increased symptoms. The drainage from the nose and sinuses is known as post-nasal drip. To understand sinusitis, it is critical to also understand the sinuses themselves.
Sinuses
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.
This information has been approved by Todd Kingdom, MD (July 2006).
