Your beloved dog starts vomiting and goes of his food. Then he develops diarrhea before he starts having seizures. Of course, you take him to the vet and after a worrying wait, while the dog is examined and X-rayed you vet tells you the dog has been poisoned and needs an operation.

You know that you locked away all the poisonous chemicals and you never feed your dog chocolate. With the operation over the vet hands you a small pitted and blackened metallic disc. That disc was a Lincoln penny and it was poisoning your dog.

The element zinc is an essential micronutrient and dogs receive enough of this in their normal diet (normally about 80 to 120 ppm dry weight of food). It also makes up about 97 % of the metal in Lincoln pennies minted from 1983 onwards. When a dog swallows an object containing zinc the acidic gastric juices attack the metal in the stomach. This forms zinc salts, which pass from the stomach into the duodenum where they are absorbed into the body.

The irritation of the gastrointestinal tract by these zinc salts causes the vomiting and diarrhea. Unfortunately, the metal adheres to the lining of the stomach so the vomiting does not remove the source of the poison.

It is not only the intestinal tract affected by the zinc poisoning. The pancreas, liver, kidneys, bones, prostate and muscles all suffer. The zinc prevents the take up of other metal ions essential for cellular metabolism such as iron and calcium. It also affects red blood cell causing them to break down. The removal of the resulting free hemoglobin from the blood stream by the kidneys causes nephrosis.

Pennies are not the only source of metallic zinc that vets find inside dogs. Zippers, batteries, galvanized screws or nuts (sometimes from a pet carrier meant to keep a dog safe while travelling!) and those little metal counters used in children's board games all potentially contain zinc. Other, non-metallic, sources of zinc poisoning found in dogs include zinc oxide cream, shampoos, paint and even some herbal supplements.

Some dog will eat anything they find within their reach. If it contains zinc, it can kill. A dose of about 100 mg/kg body weight will kill 50% of dogs. Prompt treatment by a qualified veterinarian is essential if a dog has ingested any form of zinc

Reference Sources:

Merck Veterinary Manual

University of Georgia College of Veterinary Medicine

Learn more about this author, Alison Bowler.
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