I would not do it as garlic, along with onions, is listed on just about every list of poisonous things for dogs, as this list:
Welcome to Healthypet.com! which lists them as blood toxins. I don't know if that is just in raw form or both raw or cooked. I also don't know how much they have to get before it is toxic. But since I can find a dozen or more sites within minutes that tell me it is toxic, I am not feeding my crew any garlic.
If a person wants to stay natural to keep the fleas away, try Minksheen shampoo.
LOL! That is funny -- after I hit the post I saw Roxies mom listed the same link! Must be high on the google list! Great minds........