I spend what most people would undoubtedly consider an unhealthy amount of time thinking about the most dangerous things dogs can eat. On Dogster, I have touched on pennies, dishwasher detergent, and snail bait as common but extremely dangerous household items that can kill dogs. But I don’t think I’ve ever talked about magnets.

Magnets come in many varieties. There are basic weak refrigerator magnets that often portray photographs or company logos. Your veterinary office may have provided you with one of these, and it might be stuck, harmlessly I’m happy to say, to your fridge. Although dogs can always find a way to get themselves into trouble with any household item, weak ordinary refrigerator magnets are not necessarily any more dangerous than any other potential foreign body.

The magnets I’m talking about in this post are so-called rare earth magnets. In particular, neodymium magnets are noted for the danger they pose to dogs.

Neodymium magnets have been popular for about 20 years. They are super strong. They often are shaped as discs, and they adhere to refrigerators and to each other with great force. They also often are used as toys. They can be thrown toward a refrigerator from a great distance, and they almost always will stick. They can be stacked into long chains that adhere to the fridge or to any other appropriate metal object. And they are really, really dangerous to dogs.

Neodymium magnets aren’t especially toxic. And, in fact, a dog might be able to eat and pass one of them without suffering from any serious adverse effects. But when a dog eats more than one of the super powerful magnets, trouble is very likely.

Imagine this scenario: A dog eats several neodymium magnets. The magnets start to pass through the intestinal tract. As I mentioned, the magnets have very strong affinities for each other. The intestines loop back and forth in the abdomen. As they separately pass through the intestinal loops, two of them might come into proximity to each other even as they are in separate intestinal loops. The result is a catastrophe.

The two magnets will bind to each other, despite the fact that two intestinal walls separate them. They will lodge in place, potentially causing an intestinal obstruction.

But an intestinal obstruction is the least of a dog’s concerns when this happens. Because of their strength, the magnets will create significant pressure on the sections of intestinal wall that separate them. This will compromise blood flow to the segments in question. The affected segments rapidly die and fall apart. This exposes the magnets — along with massive quantities of bacteria, food, and intestinal juices, to the inside of the abdomen.

When this phenomenon — called intestinal perforation — occurs, fatal consequences often soon follow. A raging bacterial infection will occur in the abdomen, leading to a condition called septic peritonitis. Dogs rarely survive long with septic peritonitis, and emergency surgery is necessary in such cases. Even with surgery, fatal consequences can occur.

What, you may ask, is the danger if a dog swallows a chain of neodymium magnets that are already bound together? Since they won’t be traveling through the intestines individually but instead as a chain that acts like a single item, might they pass without incident?

They might. Or they might not. The March 1, 2015, issue of the Journal of the American Veterinary Medical Association (JAVMA) contained a harrowing case study that illustrates just how dangerous these magnets are. A three-year-old Yorkshire Terrier was suspected to have consumed a chain of neodymium disc magnets. As the chain passed from the esophagus into the stomach, it bent back upon itself and bound to itself, causing it to lodge at the junction between the two structures.

The result was a disaster. The esophagus perforated, and infected fluid filled the chest. This lead to compression of the lungs and difficulty breathing. The fluid was drained, and during exploratory surgery the magnets were removed. However, surgery revealed further perforations in the stomach. The surgeons worked to repair the defects in the esophagus and the stomach.

The dog initially recovered from surgery, but died of acute cardiac arrest 48 hours later. This incident, for your information, did not occur at a neighborhood veterinary clinic. The dog was treated at the Tufts University Veterinary Teaching Hospital, where he no doubt received the best possible care.

The moral of the story is this: If you have a dog, you should not have neodymium magnets in your house. If you don’t follow this rule and you suspect that your dog may have consumed strong magnets, seek immediate veterinary attention. Endoscopy often can lead to safe removal of the offending objects if the problem is caught within the first few hours.

As an aside, it should be noted that our canine companions are not the only ones for whom neodymium magnets are dangerous. The magnets are well known to be similarly dangerous to children.

Learn more about dog health from Dr. Eric Barchas:

• What Causes Acute Anemia in Dogs?
• What Causes Puppy Mange and How Can It Be Treated?
• How One Penny Cost a Dog’s Family Thousands of Dollars

Got a question for Dr. Barchas? Ask our vet in the comments below and your topic might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)