VETERINARIANS do not like giving dogs any kind of “people food” but are especially serious about keeping chocolate far away from our canine friends. 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. 

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.

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. 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. 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.

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. Depending on the severity of the poisoning, medication or fluids may be required to counteract the poisoning.

How a dog reacts to chocolate can depend on the animal’s size. 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).

Milk chocolate is less dangerous than baking chocolate because it contains less stimulants, but if your dog has ingested any type or amount of chocolate, you are always better off being safe than sorry. 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. 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. By Manny Palomar, PhD (EV Mail October 3-9, 2022 issue)