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Antifreeze poisoning

30th July 2018

Antifreeze poisoning

In the Northern hemisphere, the onset of winter and low/sub-zero temperatures brings about an increase in the number of cats poisoned by antifreeze.

Most antifreeze solutions (used often in cars in the winter) are based on a product called ethylene glycol. The problem with ethylene glycol is that it can be very toxic when ingested, often causing rapid and frequently fatal injury to the kidneys.

All animals (including humans) are susceptible to ethylene glycol poisoning, but cats are more susceptible than most due to differences in their metabolism. These differences mean that even a very small amount of ethylene glycol if swallowed, can be fatal.

It is therefore vitally important to take great care when using ethylene glycol. It should only ever be used in closed systems (such as car engine coolant systems) and never be used elsewhere (such as in ornamental ponds or fountains to prevent them freezing – cats, dogs and other wildlife can be readily poisoned and killed by drinking from these contaminated sources). Bottles containing ethylene glycol should be stored carefully and tightly closed. Any coolant drained from a car should be disposed of carefully and any ethylene glycol spilt on the floor should be mopped up thoroughly.

If you are worried that your cat may have swallowed some ethylene glycol (or even licked its paws or fur if it may have come into contact with ethylene glycol) you should take your cat to the vet immediately as the sooner a cat is treated the better its chances of survival.

How to avoid accidental poisonings:

  • Never add antifreeze to garden water-features or ponds.
  • Always keep antifreeze in clearly labelled, robust, sealed containers, away from pets and their environment.
  • Clean up any spills immediately, no matter how small, and make sure pets cannot access the area until it is clean and safe.
  • Always dispose of antifreeze safely and responsibly. Contact your local authority for advice.

Signs of antifreeze poisoning:

  • Increased urination
  • Increased drinking
  • Vomiting
  • Depression
  • Lethargy (being abnormally sleepy)
  • Appearing drunk and uncoordinated
  • Seizures (fitting)
  • Abnormally fast heartbeat
  • Very fast, shallow breathing
If your pet shows any of these signs take them to a vet immediately.
The sooner veterinary treatment is received, the better their chances of survival. If left untreated pets can suffer, and will die.


Alternative agents

Unfortunately, ethylene glycol is almost universally used as an antifreeze agent, despite being so toxic, and there are few alternatives. It is possible to obtain propylene glycol based antifreeze in some regions, and this represents a safer alternative (although more expensive and still not completely safe).

Adding agents that taste bitter

It has been suggested that all antifreeze solutions should contain an additive, such as Bitrex®, or denatonium. Denatonium is a safe chemical that is said to be the most bitter tasting chemical known and can be added to potentially poisonous substances to make it less likely that they will be eaten or drunk.

While this sounds like an ideal solution to the problem of cats and other animals drinking ethylene glycol, in fact, denatonium (or Bitrx®) has not been shown to be very effective in discouraging dogs from eating palatable foods, and in humans, adding denatonium to antifreeze solutions has apparently not decreased the frequency of poisoning among young children. Thus while adding denatonium to antifreeze will do no harm, it may well not have the desired effect in preventing animals drinking or licking the solution.

The best advice, therefore, is to be highly vigilant and to prevent animals and children coming into contact with ethylene glycol, and if they do, to get them treated as soon as possible

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