Thanks everyone! I think I'm going to try maybe the garlic and tea tree oil diluted in their normal shampoo. I confess I'm a little wary about the tea tree oil after the previous post, so I'll do some additional net searches before I use it. As for the garlic I figure if the gas get to bad I'll pull them back off of it. I confess I haven't tried Sentinel since heartworms aren't a problem here, but I did try program a few years ago, but the problem is it sterilizes the females but doesn't kill them and one of my dogs has severe flea allergy, 1 bite and he's on pred's for the next 2 weeks. I've also tried frontline, but another of my dog;s is allergic to it. He started itching like mad so I had to go back and bathe him again (he was not amused) to get it off.