Iodine is, and has been since the Civil War, a great antimicrobial - it can kill bacteria, virus and fungus (many but not all) and is GENERALLY safe. Caution please, however! Whenever there is liquid discharge from an ear, there is a chance that an ear drum is perforated. Iodine is ototoxic and even a tiny bit in the middle/inner ear can cause profound hearing loss. If treating an irritation in the outer ear or ear canal, it would be much safer to use a gauze or cotton swab to carefully dab iodine on.
Sue