It's up to you whether you choose to use Thornit or not but used correctly, it is not dangerous (for preventative use, just a pinch of powder in each ear is quite enough) I have been using it for nearly 20 years now & our vets are always impressed with how clean our Cockers' ears are There is not much point mentioning remedies like Thornit to a vet - it is not a veterinary product, just a remedy used successfully by many, many dog owners for years & years.
Jane
my vet did say how lovely and clean mabe,s ears where,i didn,t tell him it was thornits,,don,t know why,,maybe i knew they would object to some point,,
but these are the same people who said there was nothing wrong with her ears,when i took her,,because she was scratching so much it worried me,at the first appointment,,suppose,its all to do with,,"i haven,t trained all these years to be told by some amateur what to prescribe"fair enough,,but,,it does work,and if it works,,don,t change it