While ear infections are common more so among children and pass quickly, adult ear infections might be signs of a more serious health problem, like ear cancer, or nasopharyngeal cancer, which is rare. An inner ear infection might be a result of inflammation, and middle ear infection is caused by fluids trapped behind your eardrum, and an outer ear infection is caused by bacterial infections. Additionally, tooth cavities, abscesses, and impacted molars will cause ear pain, and so will TMJ (the temporomandibular joint) pain, and your doctor will assess possible causes and guide you on the right treatment.