Pharyngitis is usually caused by a virus, including rhinovirus, adenovirus, Epstein-Barr virus, herpes simplex virus, influenza virus, parainfluenza virus, coronavirus, enterovirus, respiratory syncytial virus, cytomegalovirus, and human immunodeficiency virus. The most common bacterial cause is group A beta-hemolytic streptococci. Other common causes include Mycoplasma and Chlamydia. The organisms may invade the pharyngeal mucosa directly, causing a local inflammatory response. In up to 30% of cases, no organism is identified.

Complications of pharyngitis include otitis media, sinusitis, mastoiditis, rheumatic fever, and nephritis.

Pharyngitis produces a sore throat and slight difficulty swallowing. Swallowing saliva is usually more painful than swallowing food. Pharyngitis may also cause the sensation of a lump in the throat as well as a constant, aggravating urge to swallow. Associated features may include mild fever, headache, muscle and joint pain, coryza, and rhinorrhea. Uncomplicated pharyngitis usually subsides in 3 to 10 days. More than 90% of cases of sore throat and fever in children are of viral origin, and associated symptoms usually include a runny nose and nonproductive cough. Physical examination of the pharynx reveals generalized redness and inflammation of the posterior wall along with red, edematous mucous membranes studded with white or yellow follicles. Exudate is usually confined to the lymphoid areas of the throat, sparing the tonsillar pillars. Bacterial pharyngitis usually produces a large amount of exudate.