Standard antifreeze is deadly to humans and animals.
A substance in the antifreeze causes kidney failure when the body converts it to a crystal. As little as one teaspoon of antifreeze can kill a dog or cat says Dr. Jim Floyd, Extension veterinarian with the Alabama Cooperative Extension System. Many pets die or have to be euthanized because owners don't recognize signs of poisoning until it's too late. Symptoms sometimes don t show up for several days after animals have consumed antifreeze. The ideal treatment window is within the first four hours.