I have heard wonder stories about garlic. I also have clients with 3 airedales, that travel weekly to obedience shows, etc. and they have sworn by feeding garlic for years. They never have had fleas since doing this, and swear it works like a charm. I don't know how much they give their dogs...but yes..they reek of garlic....especially their breath. I always thought that garlic was toxic to dogs...but apparently not? as I see garlic powder supplements, etc. IMO, any shampoo is not going to be effective. The lasting effects are going to be extremely minimal...and you would have to be using is every other day or something crazy. I would look into the garlic if you want as natural as possible..there really is something to it.