History and exam

Key diagnostic factors

common

ear pain

Patients with acute otitis externa typically present with an acute onset of ear pain.[1] 

tenderness over the tragus, pinna, or both

Signs of ear canal inflammation include tenderness over the tragus, pinna, or both.[1] Manipulation of the ear canal is usually painful.

ear canal swelling and erythema

On physical exam, the skin of the external auditory canal appears erythematous and swollen.[1]

uncommon

granulation tissue in the ear canal (necrotizing otitis externa)

A key factor in necrotizing otitis externa.[1]

Other diagnostic factors

common

otorrhea

Discharge from the external auditory canal may be present in acute otitis externa.[1]

aural fullness

Patients may complain of a fullness in the ears.[1]

itching

Patients may complain of itchiness in the ears.[1] Scratching with matchsticks or cotton buds often precedes infection.

decreased hearing

In the absence of concomitant acute otitis media, hearing loss is usually secondary to blockage of the ear canal by swelling and/or debris.[1]

pain intensified by jaw motion

There may be pain in the ear canal and temporomandibular joint intensified by jaw motion.[1]

erythematous tympanic membrane

In addition to swelling in the external auditory canal, the tympanic membrane may appear erythematous, which can make exclusion and differentiation from acute otitis media difficult.[1]

cellulitis of the pinna and adjacent skin

There may be cellulitis of the pinna and adjacent skin.[1]

Risk factors

strong

external auditory canal obstruction

Obstruction of the external auditory canal by cerumen may promote retention of water and debris, which, in turn, may disrupt the integrity of the skin of the external auditory canal.[16] This in itself, or in the presence of additional risk factors, can cause infection. External auditory canal obstruction can also be caused by foreign bodies, a narrow ear canal, bony exostosis, or sebaceous cysts. 

high environmental humidity

Otitis externa is more common in areas with warmer weather or high humidity, or with increased water exposure from swimming.[1] This in itself may be enough to affect skin integrity and cause infection.[3] 

warmer environmental temperatures

Otitis externa is more common in areas with warmer weather or high humidity.[1] This in itself may be enough to affect skin integrity and cause infection.[3] Sweating may also increase moisture in the ear canal.[12]​​

swimming

The incidence is increased fivefold in swimmers, which is why the condition is also called "swimmer's ear".[14] It is also the most common otologic disorder in divers, affecting almost half of all active divers at least once.[17] ​The causative organisms have also been found in hot water tubs.[18]

local trauma

Trauma disrupts the integrity of the external auditory canal skin and will initiate the process of inflammation.[3][13] Local trauma can result from manual wax cleaning, use of irrigation to clean wax, and the use of foreign objects in the ear such as cotton-tipped applicators.

allergy

Most commonly from antibiotic ear drops such as neomycin.[2]

skin disease

Includes seborrheic dermatitis, allergic dermatitis, atopic dermatitis, and psoriasis.[2]

diabetes

Patients with diabetes are at higher risk for severe otitis externa; a modified treatment regimen is required for treating these patients.[1][12]​​[18]

immunocompromised

Patients who have received irradiation or those who are immunocompromised are at higher risk for severe otitis externa; a modified treatment regimen is required for treating these patients.[1][12][18]​​​

prolonged use of topical antibacterial agents

These agents may inhibit the normal flora after prolonged use in the external auditory canal, and their use is a risk factor for fungal otitis externa.[11]

weak

chemical irritants

Chemicals contained in ear medications, ear plugs, shampoo, and hair products can irritate and inflame the skin of the ear and make it susceptible to infection.[18]​

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