Sinuses are air-filled cavities in the head that are lined by mucous membranes that lead through small openings into the nasal cavity. When the mucous membranes become swollen and inflamed from infectious or allergic sources, the sinus openings into the nasal cavity become blocked. When this occurs, sinusitis develops resulting in more blockage and infection. There are two main categories of sinusitis: acute and chronic. Sinusitis is usually preceded by a cold, allergy attack or irritation from environmental pollutants. Often, the resulting symptoms, such as nasal pressure, nasal congestion, a "runny nose," and fever, run their course in a few days. However, if symptoms persist, a bacterial infection or acute sinusitis may develop. If sinusitis occurs frequently or lasts three months or longer, it may be chronic sinusitis. Dr Lisa Wilson is here to discuss your sinuses and give suggestions for how to keep a healthy sinus.