Sinus infection may be classified in at least two ways, based on the time span of the problem (acute, subacute, or chronic ) and the type of inflammation (either infectious or noninfectious). Acute sinus infection is usually defined as being of less than 30 days duration; subacute sinus infection as being over 1 month but less than 3 months; and chronic sinus infection as being greater than 3 months duration. Infected sinusitis is usually caused by uncomplicated virus infection. Far less frequently bacterial growth causes sinus infection. Noninfectious sinusitis can be caused by irritants and allergic conditions. Subacute and chronic forms of sinus infection usually are the result of incomplete treatment of an acute sinus infection
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