Otitis Externa and Painful, Discharging Ears

Otitis externa is inflammation of the outer ear. It includes all the inflammatory conditions of the auricle, external auditory canal and outer surface of the eardrum. It can be local, diffuse, acute or chronic.

Acute otitis externa affects around 10% of the population at some time in their lives with the average GP seeing about 16 new cases a year. It is commoner in hot and humid climates and 5 times commoner in swimmers. The peak prevalence is 45 to 54 for women and 65 to 74 for men. The very serious condition of necrotising otitis externa is rare and usually affects elderly diabetics or those who are immunocompromised.

It may be infectious in origin or caused by allergies, irritants or inflammatory conditions.

Skin diseases

These include:

• Seborrhoeic dermatitis
• Acne
• Psoriasis
• Atopic eczema
• Systemic lupus erythematosus

Infection

These can take many forms:

• There may be an infected hair follicle when S. aureus is the usual infecting organism. Infection is localised.
• In more general infection of the outer ear the organism may be bacterial or fungal.
• Fungal infection usually follows prolonged treatment with antibiotics, with or without steroids. Candida albicans and Aspergillus spp. are commonest.
• Herpes simplex and herpes zoster (Ramsay Hunt syndrome)
• Dermatophyte infection may occur with epidermophyton, trichophyton, and microsporum genera. Seborrhoeic dermatitis may be followed by infection with Pityrosporum or Malassezia spp.

Irritants

These include topical medications, hearing aids or earplugs:

• Aggravating or causative factors include ear trauma from foreign bodies in the ear, cotton buds, ear syringing or hearing aids. Swimmers are more susceptible especially in polluted water. Chemicals including hair spray, hair dyes and cerumenolytics as well as various skin conditions may be responsible.

Chronic otitis externa

This is a low grade infection that can last for months or years.

Malignant (necrotising) otitis externa is a life-threatening extension of otitis externa into the mastoid and temporal bones. It is usually due to P. aeruginosa or S. aureus.

The following may be a useful indicator of the most likely aetiology and hence the most appropriate treatment:

A furuncle

This is small with severe pain in the ear and local swelling of the canal. Pyrexia is moderate (less than 38°C). There may be posterior auricular lymphadenopathy. Examination with an auriscope can be very painful. If the lesion bursts there is sudden relief of pain.

Acute diffuse otitis externa

This produces a similar temperature and lymphadenopathy. Swelling is more diffuse and pain is variable with possible pruritus. Moving the ear or jaw is painful. The canal, external ear, or both, are red, swollen, or eczematous, with shedding of the scaly skin. There may be little but thick discharge in the acute stage but it can become bloody if chronic. Hearing is often impaired. Bacterial infection is common but often secondary.

Chronic diffuse bacterial infection

In this the skin of the canal is dry and hypertrophic. There is some swelling and narrowing. Excoriation with mucopurulent discharge may be seen.

Superficial fungal infection

This may have acute or subacute onset. Complaints are of itching and discomfort. Discharge is variable.

Contact dermatitis

This can be irritant or allergic. Irritant is usually insidious in onset with lichenification. Allergic forms tend to be more rapid in onset with itching,erythema and oedema. If otitis externa persists despite conventional treatment, consider allergy, usually to an aminoglycoside. Patch testing may be required.¹

Necrotising or malignant otitis externa

This is rare but very serious. It produces pain and headache of greater intensity than clinical signs would suggest. Facial nerve palsy is a red flag sign but not always present. Granulation tissue may be present at the junction of bone and cartilage. Criteria for diagnosis include obligatory and occasional features.² Obligatory criteria are:

• Pain
• Oedema
• Exudate
• Granulations
• Microabscess (when operated)
• Positive bone scan or failure of local treatment often more than 1 week, and possibly pseudomonas in culture

The occasional criteria are:

• Diabetes
• Cranial nerve involvement
• Positive radiograph
• Debilitating condition
• Old age

A ^99MTc bone scan is very important. The typical patient is either an old person with diabetes or a young person with HIV but atypical patients are not uncommon and a high index of suspicion is required.³

Other skin diseases

If seborrhoic dermatitis or atopic dermatitis are involved there will be local evidence of that disease.

Swabs are required only if there has been treatment failure or the situation looks atypical.

• Children and some adults put foreign bodies in their ears.
• Impacted wax can cause pain and deafness. Drops will make it swell and can aggravate it before removal.
• Otitis media is painful but if the drum bursts the pain ceases and a discharge follows.
• A chronic discharging ear is associated with chronic suppurative otitis media and possibly cholesteatoma.
• If the ear is swollen with a canal that bleeds readily on contact, consider malignancy.
• Pain can be referred from the sphenoidal sinus, teeth, neck, or throat.
• Barotrauma usually affects divers and less commonly those who have recently flown but it can result from a blow to the ear.
• Dermatological disease as listed above.

The aim of treatment is:⁴

• To settle symptoms
• To cure infection
• To reduce risk of recurrence
• To prevent complications

The choice of medication is based more on preference and pragmatism than evidence. If the condition is painful, then appropriate analgesia is required.

• Topical treatment is recommended, unless there is spread with cellulitis or the patient is systemically unwell.⁴
• A swollen ear canal should be packed with a wick or ribbon gauze soaked in steroid solution or an astringent to facilitate its passage along the ear canal.
• Otherwise, advise the patient to lie on one side with the affected ear up, to introduce the ear drops and to keep this position for 10 minutes.
• Treatment with an an antibacterial or corticosteroid should be for no longer than 7 days, because of risk of secondary fungal infection or possible allergy developing.
• Contact sensitivity with topically applied ear drops is most commonly due to antibiotics, especially aminoglycosides and preservatives.

Management in children is similar to that in adults.⁵

Acute otitis externa

• In furunculosis, analgesia and local heat usually suffice. An antibiotic such as flucloxacillin may be required. Drainage is rarely necessary.
• Even acute diffuse otitis externa requires attention to ear toilet. The canal must be cleared of debris and discharge as this lowers the pH and reduces the activity of aminoglycoside ear drops. It may be required several times a week. Analgesia is required. If there is an irritant or allergen it must be removed. Keep the ear dry and avoid scratching it with cotton wool buds. Avoid cotton wool plugs in the ear unless discharge is so profuse that it is required for cosmetic reasons. If used keep them loose and change often. Avoid swimming or at least prevent water from entering the ear.
• Topical medication will usually suffice and it is only if the patient is systemically unwell that oral therapy is required. Evidence of spreading infection or cellulitis requires oral antibiotics. In uncomplicated cases those who are prescribed oral rather than topical therapy are more likely to have a recurrence inside 28 days.⁶
• Topical antibiotic-steroid combination therapy is superior to steroid-alone treatment.⁷
• Acetic acid 2% eardrops can be very effective. They are available on prescription or OTC as Earcalm™. They are effective against both bacterial and fungal infection. They are less likely to cause allergy than aminoglycosides and less likely to cause superinfection than steroids but the acid does sting and this may impair compliance.
• Antibiotic drops usually contain aminoglycosides or fluoroquinolones and possibly an antifungal. Clioquinol is effective against both. They are often combined with steroid.
• A RCT of ear drops containing acetic acid, corticosteroid and acetic acid, and steroid and antibiotic showed that drops containing corticosteroids are more effective than acetic acid ear drops alone. Steroid and acetic acid or steroid and antibiotic ear drops are equally effective.⁸
• Antibiotic or steroid drops should not be used for over 7 days because of the risk of fungal infection. Allergy to an aminoglycoside may cross-react with others in that class.

Chronic otitis externa

Chronic otitis externa occurs over months or years and there has often been modification of the normal flora by treatment.

• Try to identify the cause or aggravating factors such as inadequate aural toilet, continued trauma from scratching or swimming. Poor compliance with treatment or contact sensitivity to previous topical treatment can be a problem. Excessive use of antibacterial drops can lead to fungal infection. There may be skin disease. Hearing aid, ear plugs, or anatomical problems, such as meatal stenosis should be identified.
• General measures of hygiene apply as for acute otitis externa. Topical medication is also preferred.
• If no cause is apparent, prescribe 7 days of acetic acid 2% ear drops together with corticosteroid ear drops. Treatment can be difficult and referral may be required.
• Superficial infection with aspergillus occurs in 80-90% of fungal infections and candida can also be involved. Acetic acid 2% or clotrimazole solution for 4 weeks may be tried.

Necrotising otitis externa

Necrotising or malignant otitis externa is caused by P. aeruginosa in 90% of cases. Oral and topical treatment, usually as quinolones is given for 6 to 8 weeks are usually required.

Contraindications and special considerations

Topical treatment is usually best but it is may be contraindicated if there is perforation of the eardrum. Aminoglycoside drops with perforation can be ototoxic. A Cochrane review found favourably for topical quinolones in chronic otitis externa with perforation of the ear drum.⁹

In malignant (necrotising) otitis externa, an oral quinolone may suffice but treatment is for 6 to 8 weeks.¹⁰ Evolving resistance to ciprofloxacin can be a problem.¹¹

Choice of drug

For acute otitis externa first choices for treatment include:

• For antibacterial cover: neomycin combined with betamethasone, hydrocortisone, prednisolone, or gentamicin on its own or combined with hydrocortisone. The addition of dexamethasone to polymyxin B/neomycin significantly reduces swelling and leads to significantly higher patient's ratings of treatment efficacy.¹²
• For antibacterial and antifungal cover: clioquinol plus flumetasone.

• Clinical Knowledge Summaries sees fluoroquinolones as second choice with concerns about promoting resistance.⁴

Oral antibiotics are indicated if the patient is systemically unwell or there is evidence of spreading infection.

• Flucloxacillin (or erythromycin if there is penicillin allergy) is preferred, because infection is usually due to S. aureus.

If initial therapy fails then re-consider diagnosis. If the patient develops cellulitis or cervical lymphadenopathy oral antibiotics are necessary.

Malignant otitis externa may involve the mastoid and there may be facial nerve palsy.

Most cases of otitis externa resolve within a few days of starting treatment. If malignant otitis externa is suspected, urgent referral to ENT should be made.