Yes, Garlic is toxic to dogs!
Dogs accidentally consuming the Garlic plants can show the following clinical symptoms: Vomiting, Prolonged Depression, Incoordination, Hypersalivaton, Sleepiness Or Excitation, Dilated Pupils, Low Body Temperature, Low Blood Pressure, Coma, Seizure And Death (In Rare Cases).
Garlic consumption is also toxic to Cats and Horses.
Toxic Principles Of Garlic: N-propyl disulfide.
More Info About The Garlic Plant
Scientific Name: Allium sativum
Family: Liliaceae.
Also known as: Stinking Rose, Rustic Treacle, Camphor of the Poor, Nectar of the Gods, Serpent Garlic, Rocambole.
The answer is based on information found on The American Society for the Prevention of Cruelty to Animals (ASPCA) website.