Dogs use little discretion when it comes to chewing and swallowing items, most of which will pass on through the dog's digestive system and pose no threat to the dog's health. A penny, however, can pose a threat to a dog's health when swallowed, if the penny was minted after 1982.

Prior to 1982, pennies were made from mostly copper. After 1982, pennies have been made with only copper coating them, 95% of the penny is composed of zinc. It's the zinc that poses the health threat to the dog when the penny is swallowed and becomes lodged in the digestive system.

If a dog swallows a penny made after 1982 and that penny does not pass through the dog's digestive system and becomes lodged in the stomach, the mostly-zinc penny will dissolve and release high levels of zinc into the dog's body. The high level of zinc will cause the dog's blood vessels to rupture, which can result in anemia or multiple organ failure.

While you can't always tell immediately if you dog has swallowed a penny, and you most certainly won't know the date of the penny your dog just swallowed, there are some symptoms to watch for that will indicate a problem.

Symptoms that indicate your dog has swallowed a penny are: vomiting, diarrhea, abdominal pain, pale gums, lethargy, weakness and depression. These symptoms would indicate that a penny has been swallowed, begun to dissolve and is not coming out on it's own. An emergency visit to the veterinarian is in order if your dog presents these symptoms.

If you know, or strongly suspect, that your dog has swallowed a penny, monitor him and his elimination closely for the next 24-48 hours. If the penny is passed in dog's fecal matter within a day or so, all should be well. If the penny does not pass, or you're not sure how much change your dog actually ate, take your dog to his veterinarian, it's better to be safe than sorry.