Chocolate's danger depends on the weight of your dog and the type and quantity of chocolate they consume, said Dr. Daniel J. Fletcher, an emergency and critical care specialist at Cornell University's College of Veterinary Medicine. In a small dog, even one dark chocolate Hershey's Kiss might be enough to trigger a problem. (Chocolate is also toxic to cats, he said, but cases are rare. Cats tend to be pickier about what they eat.)
It's not always easy to spot the signs, with so much candy on hand and dogs' tendency to eat the evidence (i.e., the wrappers). To a pet owner, chocolate toxicity looks pretty similar to any trick-or-treater's sugar high—they'll be hyperactive, said Fletcher. Other symptoms include panting, pacing and dilated pupils.
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The chemicals in chocolate can also trigger vomiting and diarrhea, as well as less-observable symptoms like high blood pressure and irregular heartbeat. "Those can be life-threatening," said Fletcher.
Chocolate isn't the only Halloween candy danger. Sugar-free candies and gum containing xylitol can result in seizures and liver failure, and raisins can lead to kidney failure. Even the candy wrappers themselves may obstruct the digestive tract if Fido didn't thoroughly chew his stolen treats. (When in doubt about whether or how much candy your pet has ingested, call your vet.)
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If there's good news, it's that rising bills for chocolate toxicity treatments have largely stemmed from better quality care, further improving Fido's chances of surviving his encounter with the Halloween candy bowl, Benson said. There are more effective drugs to aid vomiting pets, and more sophisticated tests to help determine the best course of treatment.
But avoiding an expensive vet bill is not hard: Just keep treats in a secure container and out of reach of curious pets.