Zinc Toxicosis in Dogs

Did you hear the story about the dog in New York named Jack that ate 111 pennies? The little guy inadvertently ingested them while wolfing down bagel crumbs — go figure. Other than the number of pennies ingested, this was a pretty typical case of canine zinc poisoning.

“Zinc?” You might be asking. “Aren’t pennies made from copper?” Not really. Pennies minted after 1982-1983 consist of 96% zinc and only 2.5% copper.

When a dog swallows pennies, or any other zinc-containing metal, stomach acid starts to leach out the zinc. The presence of zinc and foreign objects in the stomach irritate the lining of the gastrointestinal tract, causing vomiting, diarrhea, and loss of appetite, but it’s the zinc that is being absorbed into the blood stream that is the real source of trouble.

An abnormally high level of zinc in the blood causes red blood cells to burst, a condition known as intravascular hemolysis. The symptoms of intravascular hemolysis include:

  • pale and/or yellow mucous membranes and skin

  • weakness

  • rapid breathing

  • dark urine

When red blood cells burst they release hemoglobin. Free hemoglobin is actually quite toxic and damages organs that it comes in contact with. Severe or prolonged intravascular hemolysis can lead to multiple organ failure and death.

Treatment for zinc toxicosis centers on removing the source of the heavy metal. Pennies and other metallic objects can be taken out of the stomach surgically or with the use of an endoscope. In severe cases, blood transfusions, plasma transfusions, chelation therapy (the administration of substances that bind to metals and aid in their elimination from the body), and/or treatment for organ failure may also be necessary. If surgery/endoscopy has to be delayed while a patient’s condition is stabilized, antacids can be given to reduce the acidity of the dog’s stomach contents and limit the absorption of more zinc.

Small dogs are at highest risk for zinc toxicosis, not simply because it takes less zinc to make them sick but also because pennies tend to be unable to exit the stomach through their small pyloric sphincters (the “gate” between the stomach and small intestine). When a large dog eats pennies, they can pass out of the stomach before the acidic environment has the time necessary to leach out dangerous amounts of zinc.

Pennies aren’t the only source of toxic levels of zinc for dogs. Any galvanized hardware (e.g., nails, nuts, or staples), plumbing supplies, jewelry, old toys, zippers, etc., can be just as dangerous. And with summer on the way, we all need to remember that many sunblocks contain zinc oxide. If a dog will eat 111 pennies while scarfing up a few bagel crumbs, others would certainly consider a pina-colada scented tube of lotion worth a try.

Dr. Jennifer Coates

Image: TO / via Shutterstock