External Otitis (Otitis Externa)

Definition and epidemiology

Otitis externa is inflammation of the skin and subcutaneous tissue of the external ear canal, which may extend to the pinna and eardrum (Wiegand et al., 2019). The main clinical forms are acute diffuse otitis externa (‘swimmer’s ear’), localised otitis externa or furuncle (an infected hair follicle in the cartilaginous canal), otomycosis (fungal infection), chronic and eczematous otitis externa, and necrotising otitis externa, which spreads to the skull base in older, diabetic or immunosuppressed patients. The necrotising form is covered in a separate entry: Necrotising (Malignant) Otitis Externa.

The lifetime prevalence of otitis externa is estimated at about 10%; Dutch and UK data give an annual incidence of around 1%, and it is about five times more common in swimmers (Wiegand et al., 2019). In the United States about 2.4 million visits were recorded in 2007, roughly one for every 123 people, and 44% took place between June and August (Rosenfeld et al., 2014). Otomycosis is found in 9-30% of patients with signs and symptoms of ear canal infection (Bojanović et al., 2023).

Symptoms and signs

Acute otitis externa comes on quickly, with symptoms usually established within 48 hours. The main complaints are earache (otalgia), itching, fullness and reduced hearing, and the pain may worsen with jaw movement. Examination shows marked tenderness when the tragus is pressed or the pinna pulled, diffuse oedema and redness of the canal, discharge (otorrhoea) and debris, sometimes with enlarged regional lymph nodes (Rosenfeld et al., 2014). If swelling closes the canal, the eardrum cannot be seen and a conductive hearing loss develops.

In otomycosis itching, discharge and a blocked sensation dominate and pain is usually mild (Bojanović et al., 2023); white, cotton-like or grey-black speckled fungal debris may be seen in the canal. Chronic otitis externa is defined by symptoms lasting more than three months or more than four episodes a year; itching is the main complaint and pain is uncommon. In the seborrhoeic form the canal skin is dry and scaly with little wax, whereas in the eczematous form it is moist and red (Wiegand et al., 2019).

Causes and risk factors

About 98% of acute otitis externa is bacterial. The commonest organisms are Pseudomonas aeruginosa (20-60%) and Staphylococcus aureus (10-70%), and mixed infection is frequent (Rosenfeld et al., 2014). Fungi are an uncommon cause of acute disease but more frequent in chronic forms, and long-term antibiotic use, immunosuppression and diabetes predispose to fungal infection (Wiegand et al., 2019).

Anything that disrupts the protective layer of the canal increases the risk: swimming and prolonged water exposure, minor trauma from cotton buds or scratching, skin conditions such as atopic dermatitis and psoriasis, diabetes and immunosuppression (Wiegand et al., 2019). For otomycosis, a hot and humid climate, overuse of antibiotic drops and headphone use are also listed as predisposing factors (Bojanović et al., 2023). In 87 patients with otomycosis in Türkiye, the commonest predisposing factors were wearing head coverings (74.7%), fungal skin infection (34.5%) and swimming (27.6%), and the commonest organism was Aspergillus niger (44.8%) (Ozcan et al., 2003).

Earmoulds and in-the-ear devices occlude the canal, raising humidity and temperature, hindering wax clearance and causing minor trauma where the mould rubs. Wearing a hearing aid with an occlusive mould is listed among the predisposing factors for otomycosis (Bojanović et al., 2023). In people using a hearing aid in one ear, debris and microorganisms were significantly more common in the aided than in the unaided ear, and intolerable itching was associated with bacterial and fungal otitis externa (Orji et al., 2014). In chronic eczematous disease, irritation or contact allergy to the mould material should also be considered.

Audiological and clinical assessment

The diagnosis is based on the history and otoscopy. The AAO-HNS guideline recommends distinguishing diffuse acute otitis externa from other causes of otalgia, otorrhoea and canal inflammation, and asking about factors that modify management, such as a non-intact eardrum, a grommet, diabetes, immunosuppression or previous radiotherapy (Rosenfeld et al., 2014). The differential diagnosis includes acute otitis media and discharging chronic otitis media, furuncle, earwax impaction, foreign bodies, contact dermatitis, herpes zoster and canal tumours.

• Otoscopy: record oedema, discharge, fungal debris and, if visible, the eardrum; tests requiring a probe are postponed during active infection.
• Pure-tone audiometry: if swelling and debris close the canal, a mild conductive loss with normal bone conduction is expected. Reduced bone-conduction thresholds point to middle or inner-ear involvement.
• Tympanometry and acoustic reflexes: in the acute phase the probe is painful and canal swelling makes results unreliable, so testing waits until the ear has healed. An occluded canal gives a flat trace with low ear canal volume.
• OAE and ABR: postponed until the canal is open and dry; otherwise absent responses may simply reflect canal occlusion.
• Impressions and hearing aid fitting: impressions are not taken until the infection has fully resolved, and the fit of the mould is reassessed once the canal skin has healed.

Culture is useful when there is no response to treatment, recurrent infection or immunosuppression. The guideline recommends reassessing patients who fail to respond within 48-72 hours to confirm the diagnosis and exclude other causes (Rosenfeld et al., 2014). In an older patient with diabetes, persistent severe night pain, granulation tissue on the canal floor or facial palsy are red flags for necrotising otitis externa and need urgent ENT assessment.

Treatment and audiological rehabilitation

Treatment of acute otitis externa rests on assessing pain and relieving it with analgesia, cleaning the canal and using topical drops. Topical preparations are the initial therapy for uncomplicated cases; systemic antibiotics are not started unless infection extends beyond the canal or specific host factors are present. If swelling blocks the canal, aural toilet or a wick helps the drops reach the infected skin, and a non-ototoxic preparation is chosen when the eardrum is perforated or a grommet is present (Rosenfeld et al., 2014). The choice of drug and duration rest with the doctor.

A Cochrane review showed that topical treatments are effective for uncomplicated acute otitis externa, with no clinically meaningful differences between topical options; with antibiotic-steroid drops symptoms last about six days (Kaushik et al., 2010). With appropriate treatment, 65-90% of patients improve within 7-10 days (Wiegand et al., 2019).

In otomycosis, regular microscopic cleaning of the canal and topical antifungals are the mainstay, and systemic treatment is reserved for severe or refractory cases (Bojanović et al., 2023). In the Turkish study, boric acid in alcohol combined with frequent suction cleaning was effective in 77% of patients (Ozcan et al., 2003). In chronic and eczematous forms the underlying skin disease is treated, irritants are avoided and the canal is kept dry; topical antimicrobial or steroid drops are used, topical tacrolimus has also been described, and canalplasty is indicated only if the canal has become stenotic (Wiegand et al., 2019).

For hearing aid users, whether to stop wearing the aid or shorten wearing time during the acute phase follows the doctor’s advice. After healing, the audiologist cleans the mould and aid and checks for pressure and friction points. In recurrent cases, a mould with a larger vent, an open fit, a different mould material or devices that leave the canal open (for example bone conduction implants) are considered together with the doctor.

Impact on quality of life and advice

Although acute otitis externa resolves quickly, severe pain can disrupt sleep, work and school for several days. In chronic and eczematous forms, constant itching, discharge and repeated flare-ups have a marked effect on quality of life. For hearing aid users, days without the aid make communication harder and increase listening effort; telling family and colleagues, talking face to face and using visual cues all help during this period.

Practical advice: after swimming or showering, dry the outer ear with a towel, do not put objects into the canal and avoid cotton buds. During treatment keep the ear dry unless your doctor advises otherwise, and use the drops for the recommended period with the correct technique. If you have recurrent otitis externa, ask your doctor about earplugs for swimming. Clean your hearing aid daily and store it overnight in a drying container; if your mould hurts or itches, see your audiologist. If you have diabetes, do not ignore ear pain or discharge.