Otitis externa is inflammation of the skin in the external ear canal. Oto- refers to ear, -itis refers to inflammation, and externa refers to the external ear canal. The infection can be localised or diffuse. It can spread to the external ear (pinna). It can be acute (less than three weeks) or chronic (more than three weeks).
Otitis externa is sometimes called “swimmers ear”, as exposure to water whilst swimming can lead to inflammation in the ear canal. Trauma from the ear canal (e.g., from cotton buds or earplugs) is another predisposing factor. Ear wax (cerumen) has a protective effect against infection, and the removal of ear wax can increase the chances of infection.
The inflammation in otitis externa may be caused by:
- Bacterial infection
- Fungal infection (e.g., aspergillus or candida)
- Seborrhoeic dermatitis
- Contact dermatitis
TOM TIP: Think about fungal infection in patients that have had multiple courses of topical antibiotics. Antibiotics kill the “friendly bacteria” that have a protective effect against fungal infections. This is similar to how oral antibiotics can predispose people to develop oral or vaginal candidiasis (thrush).
The two most common bacterial causes of otitis externa are:
- Pseudomonas aeruginosa
- Staphylococcus aureus
TOM TIP: It is worth remembering Pseudomonas aeruginosa. It is a gram-negative aerobic rod-shaped bacteria. It likes to grow in moist, oxygenated environments. Other than causing otitis externa, an important exam-related point to remember is that it can colonise the lungs in patients with cystic fibrosis, significantly increasing their morbidity and mortality. It is naturally resistant to many antibiotics, making it very difficult to treat in children with cystic fibrosis. It can be treated with aminoglycosides (e.g., gentamicin) or quinolones (e.g., ciprofloxacin).
The typical symptoms of otitis externa are:
- Ear pain
- Conductive hearing loss (if the ear becomes blocked)
Examination can show:
- Erythema and swelling in the ear canal
- Tenderness of the ear canal
- Pus or discharge in the ear canal
- Lymphadenopathy (swollen lymph nodes) in the neck or around the ear
The tympanic membrane may be obstructed by wax or discharge. It may be red if the otitis externa extends to the tympanic membrane. If it is ruptured, the discharge in the ear canal might be from otitis media rather than otitis externa.
The diagnosis can be made clinically with an examination of the ear canal (otoscopy).
An ear swab can be used to identify the causative organism but is not usually required.
Mild otitis externa may be treated with acetic acid 2% (available over the counter as EarCalm). Acetic acid has an antifungal and antibacterial effect. This can also be used prophylactically before and after swimming in patients that are prone to otitis externa.
Moderate otitis externa is usually treated with a topical antibiotic and steroid, for example:
- Neomycin, dexamethasone and acetic acid (e.g., Otomize spray)
- Neomycin and betamethasone
- Gentamicin and hydrocortisone
- Ciprofloxacin and dexamethasone
Aminoglycosides (e.g., gentamicin and neomycin) are potentially ototoxic, rarely causing hearing loss if they get past the tympanic membrane. Therefore, it is essential to exclude a perforated tympanic membrane before using topical aminoglycosides in the ear. This can be difficult if the patient has discharge, swelling or wax blocking the ear canal. Patients with a blocked ear canal may need to be seen by ENT to microsuction the debris from the canal and visualise the tympanic membrane. They will also require a referral if the canal is so blocked or swollen that topical treatments cannot reach the site of infection.
Patients with severe or systemic symptoms may need oral antibiotics (e.g., flucloxacillin or clarithromycin) or discussion with ENT for admission and IV antibiotics.
An ear wick may be used if the canal is very swollen, and treatment with ear drops or sprays will be difficult. An ear wick is made of sponge or gauze. They contain topical treatment for otitis externa (e.g., antibiotics and steroids). Wicks are inserted into the ear canal and left there for a period of time (e.g., 48 hours). As the swelling and inflammation settle, the ear wick can be removed, and treatment can continue with drops or sprays.
Fungal infections can be treated with clotrimazole ear drops.
TOM TIP: The treatment for otitis externa I have seen used most often is Otomize ear spray, so this is probably the one to remember. Always check the local antibiotic guidelines when prescribing antibiotics, as they will vary in different hospitals and areas.
Malignant Otitis Externa
Malignant otitis externa is a severe and potentially life-threatening form of otitis externa. The infection spreads to the bones surrounding the ear canal and skull. It progresses to osteomyelitis of the temporal bone of the skull.
Malignant otitis externa is usually related to underlying risk factors for severe infection, such as:
- Immunosuppressant medications (e.g., chemotherapy)
Symptoms are generally more severe than otitis externa, with persistent headache, severe pain and fever.
Granulation tissue at the junction between the bone and cartilage in the ear canal (about halfway along) is a key finding that indicates malignant otitis externa.
Malignant otitis externa requires emergency management, with:
- Admission to hospital under the ENT team
- IV antibiotics
- Imaging (e.g., CT or MRI head) to assess the extent of the infection
It can lead to complications of:
- Facial nerve damage and palsy
- Other cranial nerve involvement (e.g., glossopharyngeal, vagus or accessory nerves)
- Intracranial thrombosis
Last updated July 2021