What are the non‑acute otitis media causes of tympanic membrane erythema?

Non-AOM Causes of Tympanic Membrane Erythema

Tympanic membrane erythema without middle ear effusion or bulging most commonly results from acute otitis externa, viral upper respiratory infections, crying, cerumen removal attempts, or dermatologic conditions affecting the ear canal—not acute otitis media. 1, 2

Primary Differential Diagnoses

Acute Otitis Externa (AOE)

• AOE can mimic AOM because erythema extends to involve the tympanic membrane, but the key distinguishing feature is tragal or pinna tenderness on examination 1
• Pneumatic otoscopy demonstrates good tympanic membrane mobility with AOE (normal type A tympanogram) versus absent/limited mobility with AOM (flat type B tympanogram) 1
• Look for diffuse ear canal edema, erythema, or discharge on otoscopy—these findings localize the pathology to the external canal rather than middle ear 1
• Predisposing factors include water exposure, dermatologic conditions (eczema, seborrhea, psoriasis), trauma from cotton swabs, hearing aids, or earplugs 1

Viral Upper Respiratory Infections

• Viral infection of the nasopharyngeal and Eustachian tube epithelium causes tympanic membrane erythema without bacterial middle ear infection 1
• Approximately 5% of middle ear effusions contain only viruses, and viral URTI can produce TM erythema through inflammation without bacterial AOM 1
• Erythema from viral infection typically presents with concurrent upper respiratory symptoms but without the bulging or cloudy appearance characteristic of bacterial AOM 2

Mechanical/Iatrogenic Causes

• Crying, fever, or vigorous attempts to remove cerumen produce isolated tympanic membrane erythema and should not be the sole basis for diagnosing AOM 2
• These causes result in vascular engorgement without middle ear pathology 2
• A distinctly red tympanic membrane increases likelihood of AOM (adjusted LR 8.4), but normal erythema alone without bulging, cloudiness, or immobility is insufficient for diagnosis 3

Dermatologic Conditions

• Eczema (atopic dermatitis) and seborrheic dermatitis commonly involve the ear canal and surrounding tissue, producing erythema that extends to the tympanic membrane 1
• Patients present with chronic pruritus, often with involvement of multiple body areas and characteristic skin findings (xerotic scaling, lichenification, hyperpigmentation) 1
• Management requires topical corticosteroids and emollients rather than antibiotics 1

Critical Diagnostic Approach

Essential Examination Techniques

• Perform pneumatic otoscopy to assess tympanic membrane mobility—this is the single most important maneuver to distinguish AOE/viral causes (mobile TM) from AOM (immobile TM) 1
• A bulging, cloudy, and immobile tympanic membrane together are highly associated with true AOM (adjusted LR 34-51) 1, 3
• Test for tragal/pinna tenderness—its presence indicates external canal pathology (AOE) rather than middle ear disease 1, 4

Key Pitfalls to Avoid

• Do not diagnose AOM based on erythema alone—this leads to massive overdiagnosis and inappropriate antibiotic prescribing 2, 3
• Ensure adequate visualization by removing cerumen; an obstructed view prevents accurate assessment of TM mobility, color, and position 1, 2
• Isolated erythema without bulging, cloudiness, or impaired mobility does not meet diagnostic criteria for AOM and should prompt consideration of alternative diagnoses 1, 2, 3

Additional Considerations

Otitis Media with Effusion (OME)

• OME presents with middle ear fluid without signs of acute inflammation—the TM may appear retracted or have an air-fluid level but lacks the intense erythema and bulging of AOM 1
• Distinguishing OME from AOM is critical because OME does not require antibiotics 1
• Tympanometry showing flat tracing (type B) with minimal erythema suggests OME rather than acute bacterial infection 1

Chronic/Structural Causes

• Myringosclerosis, retraction pockets, and tympanosclerosis can produce TM discoloration or erythema without acute infection 5
• Almost half of temporal bones with middle ear pathology show no associated tympanic membrane changes, emphasizing that TM appearance alone is insufficient for diagnosis 5
• Chronic suppurative otitis media with perforation produces erythema and discharge but represents a distinct entity requiring different management 1, 6, 7