I think if you gave them bulb after bulb then yeah they'd get very ill indeed, but then again so would a human.

Someone in the USA has patented a dog breath ameliorator,

To quote The New York Times 25th March 2002

"So Ms. Lewandowski did some experimenting with her dogs to tease out the crucial ingredients. She fed them ground beef sautéed in olive oil and onions, beef patties broiled with sage and hamburger cooked in canned tomatoes (on the theory that tomatoes, renowned for their ability to soak off skunk spray, might also freshen breath).

She found no discernible improvement in the dogs' breath, however. Then she tried sprinkling the ground beef with garlic powder. And voilà.

Ms. Lewandowski says she has confirmed her results over several years in about 30 dogs. A dose of garlic powder sprinkled on a meal leaves a pet's breath fresh for up to 72 hours, she said.

She cautions that it is important to have the appropriate dosage"

Appropriate dosage, meaning 1/2 clove per 10lb's of dogs body weight, as she consulted Mary L Brennan DVM.
I've scoured the internet for how much is too much garlic and the general concencous seems to be that a dog would have to eat an awful lot of garlic before it became as ill as if it'd eaten a cup full of chopped onion.

I did read an interesting paper and then my toddler decided to switch off the PC where a dog had eaten rasins, garlic and some other things, the poison it died from was from raisins, the vets ruled out the garlic as the poison. I'll try to find the link again from my history but not doing it this minute.

Eola - you haven't been giving anyone strange coffee have you?