Otitis Externa

Otitis externa pathophysiology centers on disruption of the ear canal's natural defense mechanisms. Cerumen provides a hydrophobic, acidic (pH 6.1) barrier containing lysozymes and antimicrobial peptides that inhibit microbial colonization. The ceruminous glands produce lipids that maintain skin moisture and barrier function, while normal epithelial migration moves debris laterally. Water exposure disrupts the cerumen barrier, raises canal pH toward neutral, and creates a warm, moist environment ideal for bacterial proliferation. Pseudomonas aeruginosa thrives in this alkaline, moist environment and is the predominant pathogen in swimmer's ear. In diffuse OE, bacterial invasion of the canal skin triggers inflammatory edema, narrowing the canal and trapping debris. Classification includes diffuse OE (swimmer's ear), acute localized OE (furuncle), necrotizing OE (extends to temporal bone), and otomycosis (fungal—Candida, Aspergillus). Necrotizing OE is a life-threatening condition primarily affecting diabetic and immunocompromised patients where infection invades the temporal bone, skull base, and potentially the intracranial cavity. The nurse performs comprehensive assessment, differentiates OE from other otic conditions, manages topical therapy protocols, and identifies patients at risk for necrotizing disease.