Acute otitis externa (AOE) is the acute onset of inflammation of the external auditory canal, which may involve the pinna and tympanic membrane. AOE classically has a rapid onset, symptoms of ear canal inflammation, and findings of ear canal inflammation. Symptoms of otitis externa include otalgia, itching, fullness, or ear canal pain with chewing. The hallmark physical finding of AOE is intense tenderness and pain of the tragus and/or pinna with movement. Otitis externa is common with an incidence of 1:100 to 250 in the general population and peaks between 7 and 12 years of age. Otitis externa is a cellulitis of the external ear with acute inflammation and edema, and bacterial organisms account for 98% of cases. The most common pathogens are Pseudomonas aeruginosa, Staphylococcus aureus, and polymicrobial infections. Gram-negative organisms (excluding Pseudomonas) account for no more than 2% to 3% of cases and fungal infections are a rare cause of primary AOE.

The treatment objective in otitis externa is to eradicate the pathogens responsible for the infection and reduce ear pain. Topical antibiotics are the most beneficial and efficacious for the treatment of AOE. Topical antibiotics are recommended for the initial treatment of diffuse uncomplicated AOE. Oral antibiotics are often prescribed in addition to topical antibiotics but have limited efficacy against P. aeruginosa and S. aureus. Topical therapy allows for a high concentration of antimicrobial that exceeds the minimal inhibitory concentration needed for pathogen eradication and has little systemic absorption, thus limiting systemic side effects. Furthermore, there are lower persistence and recurrence rates with topical antimicrobials.