Your pocket can hold many potentially lethal items, so let me be more specific:

‘What’s the Dog Killer in Your Pocket That You Wish No Longer Existed?’

Can you guess? Let’s review the clues:

  • It can be lethal to dogs

  • It can be found in your pocket

  • You wish it no longer existed

Can you guess?

Are you guessing?

Still guessing?

Got your answer?





Or, more specifically, pennies minted after 1982.

Not all pennies are created equal

Although all pennies are equal in value — one cent, no matter what day it is — their compositions are not. Pennies minted before 1982 are predominantly copper (about 95%), while pennies churned out after 1982 are mostly zinc (about 97.5%). 1982 was a transition year, and weight determines the composition — zinc pennies are comparably lighter. When dropped, copper pennies have a higher-pitched ‘ring,' while the zinc pennies carry more of a ‘clunk.’ (Dogs don’t care about any of this, but maybe you do.)

The problem with pennies

The post-1982 pennies are most troubling.* These pennies are typically described as copper-coated zinc pennies because they contain mostly zinc and have about 2.5% copper. Zinc easily corrodes in acidic environments, which is bad news for anyone who finds a penny (or pennies) in their stomach.

Zinc is an essential mineral, although undesirable in excessive amounts. According to the ASPCA Animal Poison Control Center, “The stomach’s acidic environment results in rapid release of zinc from ingested pennies. The release rate depends on the stomach’s pH, the presence or absence of food, and the length of time the pennies are in the stomach …. The toxic dose of zinc in dogs is unknown.” What is known is the rapid release of zinc is associated with the destruction of red blood cells which can result in a number of debilitating conditions including kidney or liver failure.

Unfortunately, our companion dogs don’t care about penny value or composition. Veterinary Practice News recently posted their ‘2014 X-Ray Contest Winners’ with the subtitle: ‘Animals will eat just about anything. The proof is in the radiographs.’ On the list:

  • 43 and 1/2 socks removed from a Great Dane

  • A lightbulb that ultimately passed (intact) from a Golden Retriever

  • A dog named Woof ate five rubber ducks

  • Norris, the Rat Terrier, ate a bra

  • 104 pennies removed from the stomach of Stella, the Pug

Zinc-afflicted dogs often present with severe vomiting, diarrhea, lack of appetite, pale or yellow gums, urine that’s more the color of wine, and even difficulty breathing, among other things. The good news is that many dogs can do well, particularly if it is caught early. A retrospective study of 19 cases of dogs with zinc toxicosis found that 17 survived after a hospital stay. Of course, that means two dogs weren’t so lucky.

I alert you to the variations in penny composition and the topic of zinc toxicity not to promote spontaneous panic or mass inspection of all pennies that enter your house (after all, pre-1983 pennies also carry zinc, as do a lot of other household items that dogs might consume). Instead, I want to couch penny consumption under the umbrella of a larger topic.

In the 21st century, we are increasingly investigating the effects that humans impose on the world around us. For example, researchers find that anthropogenic noises are associated with “body malformations in marine invertebrates,” and traffic noises could be behind city birds singing higher-frequency songs than their country counterparts. Companion dogs are often at our whims, from when and how they eat to whether or not they wear pantyhose. Certainly, no one was thinking about dogs when Washington approved the transition from a copper to a zinc penny. But if Abraham Lincoln were alive today, I’m sure he would say, “One score and twelve years ago, our fathers brought forth on this continent a new penny, conceived in zinc, so please keep them out of reach of your dogs. And please do not permit economic inflation that would render such pennies useless. Thank you.”


* “Because of [the] severe effects, consider all penny ingestions potentially dangerous, and treat each case aggressively" (Richardson et al. 2002).

Image: Brian Pocket; Flickr creative commons

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Do You Know a Fat Dog When You See One?

What Should I Feed My Dog?

How Do You Play With Your Dog?

Dogs in Pantyhose


Droual R. & F. D. Galey (1991). Zinc Toxicosis Due to Ingestion of a Penny in a Gray-Headed Chachalaca (Ortalis cinereiceps), Avian Diseases, 35 (4) 1007. DOI:

Gurnee C.M. (2007). Zinc intoxication in dogs: 19 cases (1991–2003), Journal of the American Veterinary Medical Association, 230 (8) 1174-1179. DOI:

Mikszewski J.S. & R. S. Hess (2003). Zinc-associated acute pancreatitis in a dog, Journal of Small Animal Practice, 44 (4) 177-180. DOI:

Richardson et al (2002). Zinc toxicosis by penny ingestion in dogs. ASPCA Animal Poison Control Center. Veterinary Medicine