Acute sinusitis most often follows a common cold which is usually of viral etiology. Vasomotor and allergic rhinitis may also be antecedent to the development of sinusitis. Obstruction of the sinusal ostia due to deviation of the nasal septum, presence of foreign bodies, polyps or tumors can predispose to sinusitis. Infection of the maxillary sinuses may follow dental extractions or an extension of infection from the roots of the upper teeth. The most common bacterial agents responsible for acute sinusitis are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Other organisms including Staphylococcus aureus, Streptococcus pyogenes, gram-negative organisms and anaerobes have also been recovered. Chronic sinusitis is commonly a mixed infection of aerobic and anaerobic organisms.