Causes of Antifreeze Poisoning
Ethylene glycol (EG) poisoning in dogs (and in cats) is almost always caused by voluntary ingestion of automotive antifreeze products, which usually contain about 95% EG. Cases of malicious poisoning with antifreeze have also been reported. When water sources are limited because they are frozen, antifreeze typically remains in its liquid form due to its lower freezing point. Leaks of antifreeze from automobile engines and radiators are the main source of antifreeze poisoning in pets. The household garage is the most common site of exposure to this toxin.
Once a dog eats or drinks antifreeze or other products that contain ethylene glycol, the toxin is rapidly absorbed into circulation from the gastrointestinal tract. Ethylene glycol can be detected in a dog’s blood within less than 30 minutes after it has been ingested. The dog’s liver then metabolizes the ethylene glycol into several highly toxic substances within a matter of hours. One of the main metabolites of EG is oxalic acid. Oxalic acid binds to calcium in the animal’s blood, causing the formation of calcium oxalate crystals. These crystals travel in the blood through circulation and ultimately lodge in the tissues of the kidneys, causing severe physical and chemical damage. This in turn leads to acute renal failure and, frequently, death. Acute renal failure is the most common cause of death from antifreeze toxicity in domestic dogs.
Prevention of Antifreeze Poisoning
The best (and only) way to prevent a dog from being poisoned by antifreeze is to keep it from coming into contact with that substance. Dogs should be kept away from garages, driveways or other areas where antifreeze may be kept, spilled or leaking. Any puddles of antifreeze should be cleaned up immediately, using kitty litter to sop up the fluid followed by copious wasing with water and detergent. Use of antifreeze products that contain propylene glycol rather than ethylene glycol is highly recommended. Propylene glycol is being called the “safe antifreeze,” because it is much less toxic to animals than ethylene glycol. Dogs should also be kept away from all other potential sources of ethylene glycol poisoning, such as paints, solvents, brake fluid, motor oil, de-icing fluids, inks, solutions used to develop photographs and wood stains.
The lethal dose of pure or undiluted ethylene glycol in an average-sized dog is about 1 to 2 teaspoons. In other words, if a dog drinks or licks 2 teaspoons or more of antifreeze that contains ethylene glycol, it probably will die a painful death from kidney failure within a matter of hours. The lethal dose is greater in large and giant breed dogs. It is important for owners to realize that it takes a very small amount of antifreeze to kill their pets.