Acute bacterial rhinosinusitis (ABRS) is caused by a bacterial infection of the paranasal sinuses. Symptoms include facial pain and pressure, purulent drainage, congestion and fever. The most common bacteria associated with ABRS include Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Almost all cases of ABRS are preceded by an acute viral rhinitis (or common cold). In the most common presentation, symptoms of a common cold develop and will resolve over the course of 7-10 days. In approximately 2-5% of cases of a common cold, ABRS develops. When this happens, the cold symptoms get worse or do not start to resolve after 5-7 days. At this point, it is appropriate to start antibiotic therapy. Starting antibiotics earlier is not recommended, since at this stage, the condition is most likely to be viral. Antibiotics do nothing for viral rhinitis and the condition is most likely to resolve without specific treatment.