thanks guys, I aked my mom when she got home(she was at a flyball tourny all weekend) she said the sheltie, collie thing is due to a defective gene, she said that they have a test now to see if the dog has that defective gene. , so if shadow does get the mange from Dakota, she will have to be tested for the defective gene first, because if she has it then the invermectin could make her very sick or even kill her(shadow is 8 years old) she is pretty healthy so she probibliy wont get it, but I told them to keep checking her just in case. I also told them that because Dakota has big droopy ears they will have to clean them periodicly after that with the rubbing alcohol/vinager mix to keep em clean, currently they are using the mix I made for them, plus Vit. E oil to help smother the ear mites.