01OverviewDefinition, clinical context and the essential points that orientate the chapter.
The external auditory canal is lined by skin whose protective surface is disrupted by scratching, water exposure, retained debris and inflammatory skin disease. Moisture and small abrasions favour microbial overgrowth, while swelling and exudate make the narrow space increasingly painful. Patients commonly describe itching first, followed by tenderness, discharge and muffled hearing. These symptoms localise imperfectly, so examination must decide whether the problem is principally in the canal, behind the eardrum or outside the ear altogether.
Diffuse otitis externa involves a broader area of canal skin. A furuncle is more focal: infection around a hair follicle produces a very tender nodule or small abscess in the outer canal. Although both can hurt when the ear is touched, their management is not identical. Drops can reach an inflamed surface, whereas a mature collection may need drainage by someone able to work safely in this confined anatomy. Squeezing or probing the lesion at home can worsen injury and should be discouraged.
Successful treatment depends on diagnosis, drug selection and physical delivery. A suitable medicine sitting on debris at the canal entrance may never reach the affected skin. Similarly, an antibiotic will not resolve continued irritation from an allergen or uncontrolled eczema. Review hearing-aid moulds, earbuds, swimming, cleaning habits and previous drop exposure. The goal is to settle the current episode while identifying the conditions that keep disrupting the skin barrier.
Key points
- Otitis externa affects the canal skin; pain on moving the tragus or pinna supports this location.
- A furuncle is a focal infected hair follicle and small abscess in the outer hair-bearing canal.
- Check the tympanic membrane and ask about perforation, grommets and previous ear surgery before selecting drops.
- Uncomplicated diffuse disease usually needs local treatment, analgesia and protection from further moisture or trauma.
- Debris and swelling can prevent delivery, so failure may require cleaning or a wick rather than another antibiotic.
- Routine oral antibiotics do not improve simple disease confined to the ear canal.
- Reassess persistent or worsening symptoms and distinguish fungal disease, contact allergy and invasive infection.
02AetiologyUnderlying causes, associations and risk factors, with why each one matters.
Barrier damage and bacterial overgrowth
Water, scratching and instrumentation can disturb canal skin and its protective environment. Pseudomonas and staphylococci are important bacterial causes, with the clinical pattern and treatment response guiding further microbiological assessment.
Dermatitis and contact exposure
Eczema, psoriasis, seborrhoeic disease and reactions to ear products or hearing-aid materials can initiate or perpetuate inflammation. Secondary infection may coexist, so treating organisms alone does not always produce sustained recovery.
Localised follicular infection
A furuncle arises in a hair follicle of the outer canal, commonly involving Staphylococcus aureus. The focal abscess differs anatomically from diffuse inflammation extending along the canal surface.
03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.
- 1Inflammation within a narrow space
Canal oedema and exudate narrow the lumen and increase contact tenderness. Obstruction can produce conductive hearing difficulty and prevent drops reaching deeper inflamed skin without appropriate clearance.
- 2The itch and injury cycle
Scratching relieves itching briefly but causes further epithelial trauma. Continued moisture, rubbing or sensitising products then sustain inflammation, allowing symptoms to recur after apparently successful antimicrobial treatment.
- 3Abscess formation in a follicle
Local bacterial invasion can produce a collection of pus around a follicle. Pressure makes the small lesion disproportionately painful; established suppuration may require a drainage assessment rather than surface therapy alone.
04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.
Ask whether itching, pain or discharge came first, and whether touching the tragus, moving the pinna or chewing increases pain. Establish swimming, instrumentation, hearing devices and recent drops. Sudden relief followed by discharge may indicate rupture of a collection or middle-ear perforation and still requires inspection.
Look at the pinna, surrounding skin and mastoid before inserting the otoscope. Identify diffuse erythema and swelling, focal pustulation, debris and discharge. Use an appropriately sized speculum without forcing it through a painful narrowed canal. Record whether the eardrum was actually visible.
A small, exquisitely tender nodule near the canal entrance supports follicular infection. Assess whether it is fluctuant, obstructing the canal or associated with surrounding cellulitis. Avoid assuming a deeper canal polyp is a simple boil, particularly when symptoms are persistent or the patient is at risk of invasive infection.
Ask about diabetes control, immune suppression, previous radiotherapy, surgery, grommets and known perforation. Document allergies, pregnancy and breastfeeding when prescribing. Examine facial movement if disease is severe or persistent, and ask about new vertigo, swallowing difficulty or headache.
05InvestigationsWhat to request, why it matters and how to interpret it.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Otoscopy and external ear examinationFirst step - Why
- Localise the disease and assess treatment safety.
- Interpretation and limitations
- The diagnosis is usually clinical. Visible canal inflammation with tenderness supports otitis externa, but an obscured membrane leaves uncertainty about perforation and middle-ear disease. Do not record an intact eardrum unless it has been adequately seen.
- 02
Culture of discharge when indicated - Why
- Investigate persistent, recurrent or atypical infection.
- Interpretation and limitations
- Routine swabbing is unnecessary in a straightforward initial episode. Obtain a specimen when treatment fails, organisms may be resistant, fungal disease is suspected or specialist assessment requires it. Interpret results alongside examination because a surface culture alone does not establish invasive disease.
- 03
Hearing assessment after obstruction settles - Why
- Check whether hearing difficulty resolves with canal recovery.
- Interpretation and limitations
- Conductive impairment can arise from debris and oedema. Persistent loss after a patent canal is restored merits audiological or ENT assessment, while sudden unexplained sensorineural loss needs an urgent pathway rather than waiting for routine infection follow-up.
- 04
Targeted blood tests and imaging - Why
- Assess systemic illness or suspected extension beyond skin.
- Interpretation and limitations
- Blood tests and scans are not routine for uncomplicated otitis externa. In suspected necrotising disease or severe spreading infection, urgent ENT assessment directs inflammatory markers, glucose testing, deep sampling and CT or MRI according to the clinical risk.
06Differential diagnosisRealistic alternatives and the features that help distinguish them.
Acute otitis media with perforation
Middle-ear infection can discharge into the canal through a perforated eardrum. Preceding respiratory symptoms, middle-ear findings and the absence of marked primary canal tenderness help distinguish the origin, although both processes can coexist.
Fungal otitis externa
Prominent itching and characteristic fungal material may follow moisture or repeated antibacterial treatment. Examination and, when needed, mycology guide cleaning and an appropriate antifungal plan instead of repeatedly extending antibacterial drops.
Necrotising otitis externa
Deep persistent pain, granulation and cranial nerve abnormalities suggest infection extending beyond canal skin. Diabetes or immunosuppression increases concern, but their absence cannot safely exclude invasive disease when the clinical features are compelling.
Referred otalgia or canal lesion
Dental, temporomandibular and pharyngeal disorders can cause ear pain with a relatively normal ear examination. A persistent focal mass or bloody discharge needs specialist assessment for structural disease rather than repeated empirical treatment.
07ManagementImmediate care, first-line treatment, alternatives and escalation.
01Uncomplicated diffuse diseaseTreat the surface and enable deliveryFirst stepCanal inflammation is present without invasive or spreading features.+
- 1Provide appropriate analgesia and choose a topical preparation after considering eardrum integrity, allergies and the likely inflammatory or infective process.
- 2Explain the administration method and review whether drops can reach the affected canal; arrange skilled clearance or a wick if significant obstruction prevents delivery.
- 3Keep the ear dry during treatment and avoid cotton buds, scratching and in-ear devices that aggravate the inflamed skin.
- 4Give a defined course and arrange reassessment if symptoms do not start improving within 48–72 hours or deteriorate sooner.
02Focal follicular infectionAssess the need for abscess drainageA localised painful canal nodule or pustule suggests a furuncle.+
- 1Assess pain, fluctuance, surrounding cellulitis and the ability to examine the deeper canal without causing trauma.
- 2Use analgesia and discourage squeezing or inserting instruments; seek ENT assessment for a large, obstructing or very painful collection that may require drainage.
- 3Use systemic antistaphylococcal treatment when clinically indicated by spreading infection or significant severity, following the local skin-infection pathway and allergy assessment.
- 4Review recurrent lesions for contributing skin disease, diabetes and microbiological factors rather than issuing indefinite repeat antibiotic courses.
03Failure or atypical courseReconsider diagnosis and escalate appropriatelyEscalationSymptoms persist despite correctly administered treatment or new warning features develop.+
- 1Re-examine the canal and membrane, check delivery and adherence, and consider contact dermatitis, fungal infection or discharge originating in the middle ear.
- 2Take appropriate microbiology and obtain ENT help for obstructing debris, persistent focal tissue or repeated treatment failure.
- 3Arrange same-day specialist assessment for disproportionate night pain, granulation, cranial neuropathy or concerning progression, particularly in an immunocompromised patient.
- 4Treat systemic deterioration as an emergency and avoid allowing outpatient swabs or a routine appointment to postpone hospital care.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Acetic acid 2% ear spray for superficial disease
EarCalm: one metered spray into each affected ear at least three times daily; maximum frequency one spray every 2–3 hours. Continue until two days after symptoms resolve, for no longer than seven days.Known or suspected perforation requires medical assessment and supervision rather than unsupervised use. Stop and seek advice for pain during use, worsening symptoms, new hearing impairment or no improvement within 48 hours. Avoid the eyes; do not extrapolate this product regimen to other ear sprays.
Dexamethasone 0.1% / neomycin 0.5% / acetic acid 2% ear spray
One metered spray into each affected ear three times daily, continuing until two days after symptoms disappear. Stop and reassess if there is no clinical improvement after seven days; avoid prolonged unreviewed courses.Do not use with a diagnosed or suspected eardrum perforation, a grommet, relevant ingredient allergy or age under two years. Aminoglycoside exposure to the middle ear can cause ototoxicity. The product is not recommended in pregnancy; agree an alternative or a breastfeeding decision with the prescriber. Stop if sensitisation develops.
08ComplicationsImportant consequences, why they occur and why they matter clinically.
Treatment delivery failure
Severe swelling or impacted debris can prevent topical medicine reaching its target. This can prolong symptoms despite an appropriate prescription and may require microsuction or placement of a medicated wick.
Spread outside the canal
Cellulitis, perichondrial involvement or a spreading abscess changes the treatment requirements. Systemic illness, marked extension or suspected deep infection warrants urgent assessment and may require systemic antimicrobial therapy.
Persistent inflammation and sensitisation
Repeated topical courses can promote contact sensitivity or select resistant organisms and fungi. A chronic itchy ear therefore needs reassessment of diagnosis and exposures, with hearing rehabilitation considered if obstruction persists.
09Monitoring and follow-upTreatment response, safety checks and longer-term review.
- Check the clinical response within 48–72 hours when improvement is absent, and sooner for increasing pain, spread, fever or neurological change.
- If a wick is inserted, provide the ear service's explicit review and removal plan; the patient should not leave it indefinitely or attempt deep canal manipulation.
- After resolution, review eczema, hearing-device irritation and water or cleaning habits to reduce recurrence without unnecessary maintenance antibiotics.
- Reassess persistent hearing loss or discharge after the canal appears healed and investigate a middle-ear or other structural explanation.
10Special situationsVariants, exceptions and circumstances that change the usual approach.
A blocked canal can mimic resistance
Failure to reach inflamed skin is a delivery problem. Confirm the route is open before concluding that a cultured organism or selected antibiotic explains continued symptoms; cleaning and a wick may be more useful than changing tablets.
An unseen membrane changes prescribing
Severe swelling may make the eardrum impossible to inspect. Combine the history with appropriate specialist assessment and choose a preparation compatible with the uncertainty. A contraindicated aminoglycoside spray is not made safe by assuming that perforation is unlikely.
Itching after treatment has several causes
Residual dermatitis, contact sensitivity and fungal overgrowth can all follow antibacterial courses. Repeated steroid-antibiotic prescriptions can mask rather than solve the problem. Inspect the skin and reconsider the trigger before deciding that another identical course is needed.
Invasive infection is a different treatment problem
Necrotising disease requires systemic treatment and specialist investigation of skull-base extension. A reduction in surface discharge does not establish that deep infection has resolved, especially when nocturnal pain or a cranial nerve abnormality persists.
11Common pitfallsFrequent interpretation and management errors.
- 01
Giving oral antibiotics alone for ordinary diffuse otitis externa without addressing topical delivery.
- 02
Using a neomycin-containing spray through a perforation or grommet despite its product contraindication.
- 03
Treating persistent severe pain in a person with diabetes as a reason simply to repeat the same drops.
- 04
Calling a granulating canal lesion a boil without considering invasive infection or another focal pathology.
- 05
Mistaking continuing contact dermatitis or fungal disease for recurrent susceptible bacterial infection.