Sinusitis occurs when the mucous membrane that lines the sinuses become inflamed. A more accurate name for the condition is rhinosinusitis. “Rhino” refers to the nose, and is a more precise name because the inflamed sinuses are usually accompanied by an inflamed mucous lining in the nose. When the mucous membranes around the openings of the sinuses become obstructed, the sinuses fill up with fluid. This warm, moist environment creates optimal growing conditions for bacteria and other microorganisms. The infection further enhances inflammation of the mucous membrane, causing a positive feedback loop that perpetuates itself.


Sinusitis causes a variety of symptoms, including four common ones. The four most common sinusitis symptoms are nasal obstruction or congestion, which causes difficulty breathing. Facial pain and pressure, including sinus headaches, are also sinusitis symptoms. You may also notice discolored nasal discharge of varying thickness and a decreased sense of smell. Many people also experience a fever, fatigue, bad breath, coughing, pressure in the ears, or toothaches.

Types of Sinusitis

Acute sinusitis is a sudden onset of inflammation and lasts for four weeks or less. A typical acute sinus infection starts as a common cold that gets worse for a few days or improves for a day or two, followed by sudden worsening. Antibiotics are usually effective at treating acute sinusitis. Chronic sinusitis involves symptoms that last for 12 weeks or longer. The condition may flare up with periods of worsening symptoms. A recurrent acute sinus infection happens when a person experiences four or more bacterial sinus infections in one year. When underlying chronic sinusitis is not present and symptoms totally clear between infections, exams are usually normal with negative CT results.

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Causes of Sinusitis

Medical experts estimate that 50 million people in the United States experience sinusitis each year. This number is believed to be increasing at a steady rate because of increased air pollution, urban sprawl, and resistance to common antibiotics. There are many causes of sinusitis. These causes include anatomical issues, genetic concerns, environmental factors, and other medical conditions. In many people, a combination of these factors contributes to the development of inflamed sinuses.

It is not always possible to determine a cause of every case of sinusitis. Some anatomical factors causing sinusitis include variations in the development of sinus cells. A deviated septum narrows sinus drainage pathways. Common environmental factors include pollution from tobacco smoke and chemicals. Allergens such as pollen, mold, dust mites, and pet dander can also trigger it.

Genetic causes include ciliary dyskinesia and cystic fibrosis. Patients can also have specific genes involving the immune system or mucous production, and further research is needed. A variety of medical conditions either contribute to or are associated with inflamed sinuses. More than one-third of people with asthma also have sinusitis. People with compromised immune systems because of poorly controlled diabetes, infection with the human immunodeficiency virus, or recent chemotherapy may experience more sinusitis. Tissue growths such as polyps and tumors also cause sinusitis.