Other medical problems can lead to symptoms similar to those encountered in otitis externa. It is important to exclude these conditions before establishing a definite diagnosis. Examples are: Atopy is caused by an allergy. Cats with itchy skin disease caused by an allergy commonly have otitis externa.
Autoimmune disease, such as systemic or discoid lupus erythematosus or pemphigus
Foreign bodies such as foxtail awns
Ear disease like cancer, hyperplasia or polyps
Parasites like ear mites, which are responsible for 50 percent of otitis in cats
Tumors. The following have been reported: squamous cell carcinoma (more common in cats than dogs), histiocytomas, sebaceous gland adenomas, adenocarcinomas, basal cell tumors, mast cell tumors, chondromas, chondrosarcomas, trichoepitheliomas, apocrine gland adenomas, fibromas, fibrosarcomas, and papillomas.