Antifreeze is a common poison. It has a sweet taste and pets will consume it readily. A little more than 3 tablespoons could be lethal for a 22 pound (10 kg) dog.
Antifreeze poisoning causes nervous systems signs and severe kidney failure. It can be fatal if not treated very soon after ingestion (within 4 to 8 hours). Pets that have ingested antifreeze may act "drunk" within 30 minutes to 12 hours after ingestion, depending on the amount ingested.
For more information, please read the article Ethylene Glycol Toxicosis.