Allergic or contact dermatitis involving the external auditory canal
- Many substances can cause a local reaction that mimics otitis externa with ear discomfort, external auditory canal discharge, canal erythema and edema (eg, neomycin, benzocaine, propylene glycol otic preparation preservative, shampoos, detergents, hair sprays, hearing aid molds)
- The aminoglycoside neomycin carries a high risk of allergic sensitization; up to 15% of otherwise healthy individuals develop contact sensitivity to neomycin and up to 30% of individuals with chronic or eczematous otitis externa develop sensitivity
- Contact and allergic reactions are often more pruritic than painful; allergic reactions for otic drops present with characteristic examination findings including a patterned rash with accentuation in the conchal bowl and erythematous streak extending from the external auditory meatus (ie, drip pattern)
- Differentiate diseases based on clinical presentation and clinical course; skin patch testing can definitively identify the cause of allergic contact dermatitis if the diagnosis remains in question
