Majority of cases in adults and children are of viral etiology.
Duration of symptoms more than 10 days often indicates bacterial cause.
Imaging is not required for diagnosis unless complications are suspected.
Condition is usually self-limited; however, symptomatic therapy is recommended.
Antibiotics are only recommended in select patient groups (e.g., immunocompromised or with severe disease).
Acute sinusitis (also commonly known as acute rhinosinusitis) is a symptomatic inflammation of the mucosal lining of the nasal cavity and paranasal sinuses, where clinical symptoms have been present for 4 weeks or less. It can be caused by either a viral or a bacterial infection. 
Health Services Research
Department of Otolaryngology-Head and Neck Surgery
University of Michigan
MAP declares that she has no competing interests.
Division of Otolaryngology and Ophthalmology
Rancho Los Amigos National Rehabilitation Center
GHS is a writer for Medscape from WebMD.
Dr Melissa A. Pynnonen and Dr Gordon H. Sun would like to gratefully acknowledge Dr Joseph K. Han, a previous contributor to this monograph. JKH declares that he has no competing interests.
Instructor of Otology and Laryngology
Harvard Medical School
Massachusetts Eye and Ear Infirmary
Department of Otolaryngology - Head and Neck Surgery
BSB is a co-founder and equity shareholder in Luxxeal, Inc.
Academic Medical Center
CG declares that he has no competing interests.
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