Chronic sinusitis and allergic rhinitis: at the nexus of sinonasal inflammatory disease.

Allergic rhinitis and sinusitis are two very common diseases that affect the health of the American people and lead to a large amount of health care expenditure. Clinical observations support the close connection between these two diseases. We review existing evidence of the link between these two diseases, stressing the similarities in inflammatory responses between allergic rhinitis and sinusitis. Possible mechanisms underlying these relationships are described.