
Aanother possibility is blocked anal glands, or a fungal/bacterial infection in the are, perhaps related to the ear trouble. Something that is unlikley to do any harm is Hibiscrub diluted in 10 parts warm water and used to wash the area and then rinse with clean water and dry. thsi will kill any fungus or bacteria. This is the wash that Vets and doctors use to srub with bto be sterile before operating.
You can get it at the vets or chemist, may have to order it, butit is inexpensive. I use it to clean any minor wounds, skin abrasians hot spots etc.