Sinusitis is an inflammation of the mucous-lined cavities that are located inside the cranial and facial bones that surround the nasal cavity. This condition can be of viral, bacterial or allergic origin. In all cases, people suffering from sinusitis are subject to irritation of the mucous membranes as well as an abnormal secretion of mucus. It is possible to distinguish several types of sinusitis, depending on which facial areas are affected by the disease. These include frontal sinusitis, maxillary sinusitis and sphenoid sinusitis. In addition, the disease may either be acute or chronic.