Veterinarians frown upon giving dogs any kind of "people food" but are especially adamant about keeping chocolate far away from our canine friends. During holidays such as Easter, when delicious chocolate may be more commonly found around the house, it's even more important to be vigilant about your pet gulping down this human treat.

But why is chocolate — milk or dark — so toxic for dogs?

Chocolate contains the chemicals theobromine and caffeine, and these two stimulants — which dogs can't metabolize as easily as people can — accumulate in the animal's body, where they can rev up a dog's bodily functions and cause dangerous side effects, according to VCA Animal Hospitals.

The severity of chocolate's negative impacts on a dog are determined by the levels of theobromine and caffeine in the chocolate product, how much of it the dog ate, and the dog's weight and sensitivity to chemical stimulants. Chocolate that is dark and bitter is more toxic to dogs, as it contains a higher concentration of theobromine per ounce than milk chocolate (130 to 450 milligrams per ounce, compared with milk chocolate's 45 to 58 mg per ounce). White chocolate, on the other hand, contains just 0.25 mg of theobromine per ounce, and therefore poses a much lower toxic threat to dogs, according to VCA Animal Hospitals.

What are symptoms of chocolate toxicity in dogs?

Initial symptoms of chocolate toxicity typically appear within 6 to 12 hours, and may include excessive drooling and panting, increased thirst and urination, and an upset stomach followed by vomiting and diarrhea, according to the American Kennel Club (AKC). The dog may experience an increased heart rate and become restless, nervous and excited, much like a caffeine-sensitive person who has downed too many cups of coffee.

In severe cases, irregular heart rate from chocolate consumption can reduce circulation, resulting in a drop in body temperature. Extreme symptoms include lethargy, muscle spasms, seizures and coma, sometimes leading to death, according to VCA Animal Hospitals. And because theobromine has a long half-life, which means it takes longer for the body to break it down, symptoms of chocolate poisoning can persist for days.

In some cases, dogs consume chocolate but show no symptoms; that's because the dosage size of the toxins can affect an animal's response to being poisoned, according to the Office for Science and Society at McGill University in Ontario, Canada.

How do veterinarians treat chocolate poisoning?

Veterinarians typically treat chocolate toxicity by inducing vomiting or administering doses of activated charcoal, which purges toxins from the dog's digestive system before they can be absorbed by the animal's bloodstream, according to the AKC. Depending on the severity of the poisoning, medication or fluids may be required to counteract the poisoning, the AKC says.

What might affect a dog's reaction to chocolate?

How a dog reacts to chocolate can depend on the animal's size, said veterinarian Dr. Greg Nelson, Director of Surgery and Director of Diagnostic Imaging at Central Veterinary Associates in Valley Stream, New York. A square of chocolate will therefore have a more pronounced effect on a Chihuahua, which typically weighs about 4 to 6 pounds (1.8 to 2.7 kilograms) than on a Saint Bernard, which can weigh as much as 180 pounds (81.6 kg).

"One hundred milligrams of theobromine and caffeine per each kilogram of a dog's weight is enough to be lethal," Nelson told Live Science. (A kilogram equals 2.2 pounds.) "Different chocolate products have varying levels of theobromine and caffeine, and the worst offender is baker's chocolate. In my experience, one ounce of baker's chocolate per kilogram [of the dog's body weight] can be lethal."

Milk chocolate is less dangerous than baking chocolate because it contains less stimulants, but Nelson warns that if your dog has ingested any type or amount of chocolate, you are always better off being safe than sorry.

Related mysteries

—Why do dogs bury bones?

—Why do dogs have cold noses?

—Are dogs really smiling at us?

"I advise clients to come in instead of second-guessing and possibly creating an emergency by not having the dog looked at right away," Nelson said. "At the very least, call your veterinarian or the national Animal Poison Control center for advice." (The American Society for the Prevention of Cruelty to Animals (ASPCA) Animal Poison Control Center can be reached 365 days a year at 888- 426-4435.)

While chocolate poisoning may affect dogs at any time, pups are more likely to find and consume chocolate on holidays such as Christmas and Easter when plentiful chocolate is available as figurines (such as bunnies and Santa Claus), as well as in bars, eggs, liqueurs, cakes and decorations, researchers wrote in a 2017 paper in the journal Vet Record. In fact, during Christmastime, dogs are four times more likely to require a vet visit for chocolate poisoning than during non-holidays; and on Easter, dogs are twice as likely to be sickened by chocolate, compared with other times of the year, Live Science previously reported.

Additional resources

Read more from the ASPCA on their Toxicology and Poison Control web page, to learn about toxins, medications, hazards and resources that could help you save the life of your pet in the event of a toxic exposure. The Veterinary Emergency Group provides tips for identifying symptoms of chocolate toxicity in dogs, and recommends what to do in an emergency. The ASPCA also compiled a list of other human foods that are hazardous for pets to eat, such as avocados, coconuts, citrus and alcohol, among others.

This article is for informational purposes only, and is not meant to offer medical advice.

Originally published on Live Science.

Bibliography

"Chocolate Poisoning in Dogs." Chocolate Poisoning In Dogs | VCA Animal Hospitals, https://vcahospitals.com/know-your-pet/chocolate-poisoning-in-dogs.

Staff, AKC. "What to Do If Your Dog Eats Chocolate." American Kennel Club, American Kennel Club, 28 Dec. 2021, https://www.akc.org/expert-advice/health/what-to-do-if-your-dog-ate-chocolate/.

"My Dog Ate Chocolate and He Was Fine, so What's the Big Deal?" Office for Science and Society, 26 Aug. 2019, https://www.mcgill.ca/oss/article/health/my-dog-ate-chocolate-and-he-was-fine-so-whats-big-deal.

Noble, Peter-John M, et al. "Heightened Risk of Canine Chocolate Exposure at Christmas and Easter." Veterinary Record, vol. 181, no. 25, 2017, pp. 684–684., https://doi.org/10.1136/vr.104762.

"Toxicology & Poison Control." ASPCApro, 21 Mar. 2022, https://www.aspcapro.org/topics-animal-health/toxicology-poison-control.

"Chocolate Toxicity in Dogs: Signs and What to Do." Veterinary Emergency Group, 21 Feb. 2022, https://veterinaryemergencygroup.com/blog/chocolate-toxicity-in-dogs/.

"People Foods to Avoid Feeding Your Pets." ASPCA, https://www.aspca.org/pet-care/animal-poison-control/people-foods-avoid-feeding-your-pets.