Chocolate was in the TOP 10 Pet Poisons for 2009.  And continues to be a main culprit in pet poisoning.  Dogs seem to be listed more than cats.  Not because chocolate is any less bad for cats, but because cats just don’t eat it as much.  Thankfully, cats just don’t have the sweet tooth dogs have.  So the good news about cats is they generally don’t want chocolate, the bad news is when they do it’s big trouble.  Their small mass is far more susceptible to toxic levels compared to your average size dog.

The entire reason chocolate is bad for pets is because of the toxic compounds called methylxanthines, specifically theobromine and caffeine.  Dogs (and cats) don’t have the same enzymes or metabolism we do, so chocolate is extremely difficult for them to digest.  The half life (once ingested) in dogs is estimated at 17.5 hours.  The lethal dose of theobromine for dogs is between 100mg to 200mg per kg of bodyweight.  However, according to the ASPCA’s Poison Control Center, symptoms appeared at 20 mg/kg, with severe symptoms at 40-50 mg/kg, and seizures at 60 mg/kg.  The amount ingested, type of chocolate, and your dog’s body weight will determine your particular dog’s fate.  See this Chocolate Chart for a better idea between the difference of: white, milk, dark, semi-sweet, bakers, & cocoa, and how it compares to your dog’s weight.

Estimated Theobromine Per Ounce of Chocolate

• White chocolate = 1 mg/oz
• Milk chocolate = 44-64 mg/oz
• Dark chocolate is = 150-160 mg/oz
• Semisweet chocolate is = 150-160 mg/oz
• Baker’s chocolate = 450 mg/oz
• Cocoa powder = 800 mg/oz

Symptoms can be seen after four hours but can sometimes take as long as 24 hours and range from vomiting, diarrhea, frequent urination, hard (to the touch) stomach area, sensitivity in the stomach area, hyperactivity, cardiac arrhythmia, seizures, and death.  Eating chocolate is very serious and you should call your vet or the ASPCA’s Poison Hotline (888-426-4435, fee applies) immediately.  Since there are so many variables, there is no specific treatment for chocolate poisoning.  Usually your medical professional will advise you to induce vomiting by hydrogen peroxide (one teaspoon per ten pounds of body weight) or syrup of ipecac, if it has been under two hours since initial ingestion.  I’m no vet but I do know hydrogen peroxide should be used sparingly in extreme emergencies because this can cause esophageal ulcers.  I would call death by chocolate a reason to use it myself, it’s the greater evil.  Activated charcoal is said to also help absorb toxins.  Your dog may have to go in and be put on fluids, treated for seizures, and/or monitored for heart failure.

If your dog gets a hold of one M&M don’t panic.  Chances are he’ll live.  Me?  I’d rather have my dog (or cat) eat zero parts per million of a known, deadly toxin.

For more information on theo­bromine and why chocolate is harmful to pets see:

“Chocolate intoxication” by Sharon Gwaltney-Brant, DVM, PhD

Merck Veterinary Manual – chocolate

“How Chocolate Can Poison Your Dogs,” Vet Info

“Leave The Chocolate Out of Rover’s Celebrations,” FDA

Hershey’s Nutrition Page – Theobromine

IARC Monographs VOL 51