Most cases are caused by a viral infection .  Strep throat is the cause in about 25% of children and 10% of adults.  Uncommon causes include other bacteria such as gonorrhea , fungus , irritants such as smoke, allergies , and gastroesophageal reflux disease .   Specific testing is not recommended in people who have clear symptoms of a viral infection such as a cold .  Otherwise a rapid antigen detection test (RAPD) or throat swab is recommended.  Other conditions that can produce similar symptoms include epiglottitis , thyroiditis , retropharyngeal abscess , and occasionally heart disease .