Last edited 09/2018 and last reviewed 05/2022

Sinusitis is the inflammation of the mucous membranes of the paranasal sinuses. However, sinusitis is almost always accompanied by inflammation of the contiguous nasal mucosa, hence a more accurate term rhinosinusitis has superseded the terms rhinitis and sinusitis (1,2)

  • usually results from inadequate drainage of the sinuses, typically the maxillary sinus ostium situated under the middle turbinate leading to obstruction with mucus retention and subsequent infection (1)
  • may occur in one or more sinuses (multisinusitis), in one or both sides (1,2,3)

It is one of the most common diagnoses in primary care. In the USA

  • sinusitis affects about 1 in 8 adults, with an annual diagnosis of over 30 million
  • it is the fifth most common diagnosis responsible for antibiotic therapy - more than 1 in 5 antibiotics prescribed in adults are for sinusitis (2)

Sinusitis is generally triggered by a viral upper respiratory tract infection, with only 2% of cases being complicated by bacterial sinusitis (1)


  1. Ah-See KW, Evans AS. Sinusitis and its management. BMJ : British Medical Journal. 2007;334(7589):358-361.  
  2. Rosenfeld RM et al. Clinical practice guideline (update): adult sinusitis. Otolaryngol Head Neck Surg. 2015;152(2 Suppl):S1-S39
  3. Amber Huntzinger .Guidelines for the Diagnosis and Management of Rhinosinusitis in Adults. American Family Physician 2007;76:10