Yorkies are susceptible to picking up sarcoptic mange. It begins as tiny white flakes along the edges of the ears, and as the dog itches and scratches then scabs can develop.
Sarcoptic Mange in Dogs
Peek A Boo contracted this from walking in wooded areas where wildlife frequented. Then, I got Scabies from him and had to go to the doctor for pymethrin creme. The vet recommended using Revolution for at least 2 months, and it prevents Heartworm too so I had to discontinue his regular HW Treatment. I didn't want to put him through that series of toxic dips to get it under control so I opted to use the Revolution. Also, sarcoptic mites don't usually show up on skin scrapings, so I saved money there. The Revolution worked within 24 hours. Poor little guy was keeping himself up at night scratching so bad, after the first application he slept for a whole day!
My other yorkie had it too when I adopted her from the Humane Society. Her ears were thickened and full of scabs. I had to put an E-collar on her to prevent her from doing further damage till the vet could see her. Once she got on the Revolution, her ears healed up within a month.
Funny thing was as I found out later, a few of my neighbors had the same problems with their dogs, and one neighbor also had Scabies. Their vet also prescribed Revolution to get it under control and eliminated. Their poor Golden Retreiver had been itching for more than a year! They and their vet thought it was allergies and was treating the dog for that.
FYI: All soaps are anti-bacterial. The ones labeled as anti-bacterial leave a residue on the skin which should not be ingested, and may cause more problems on the skin because it kills the good bacteria naturally found on the skin leaving it unable to fight off infections.