Ask the Vet: Chocolate Toxic to Dogs
Q: Our dog Riley ate a lot of semisweet chocolate bits. His veterinarian advised us to use hydrogen peroxide to make him throw up. After Riley vomited all the chocolate, he was fine.
What are the toxic effects of chocolate? How much does it take to make a dog sick?
A: Before I became a veterinarian, one of my golden retrievers ate a big bag of Hershey's Kisses. His vet gave me the same advice -- and up came all the Kisses, most still in their foil wrappers with the little paper plumes standing in salute.
Once I entered the veterinary field, I learned how dangerous chocolate can be for dogs. Part of the problem is that dogs devour chocolate until it's gone, ingesting more than even I, who love the sweet, can eat at one sitting.
Fortunately, you witnessed Riley's indiscretion and acted quickly. If you hadn't, he might have experienced significant toxicity.
The clinical signs depend on the dose and type of chocolate. Toxicity follows ingestion of cocoa powder at a "dose" of 0.01 ounces per pound of the dog's body weight, baking chocolate at 0.02 ounces per pound, semisweet chocolate at 0.06 ounces per pound and milk chocolate at 0.15 ounces per pound of body weight.
Knowing the type of chocolate ingested is important because various types contain different amounts of theobromine and caffeine, chemicals called methylxanthines (METH'-ul-ZAN'-theenes) that are toxic to dogs. Pure chocolate contains the most, while chocolate diluted with milk, sugar and other ingredients has smaller concentrations.
Cocoa powder contains 800 milligrams of methylxanthine per ounce; baking chocolate, 440 milligrams per ounce; semisweet chocolate, 160 milligrams per ounce; and milk chocolate, 60 milligrams per ounce.
Methylxanthine doses of 10-20 milligrams per pound of the dog's body weight cause restlessness, vomiting and diarrhea. At 20-25 milligrams per pound, dogs develop hyperactivity, agitation and loss of coordination. Larger doses cause rapid heartbeat, abnormal heart rhythm, tremors, seizures, coma and death.
So, a 50-pound dog that eats a 16-ounce bag of semisweet chocolate chips ingests 2,560 milligrams of methylxanthines, or 51 milligrams per pound of body weight, which may be fatal. Had the dog eaten the same amount of milk chocolate chips, he would have ingested 960 milligrams of methylxanthines, or 19 milligrams per pound, which would have been less toxic.