Chocolate (theobromine and caffeine) in Pets

How much chocolate is dangerous for a dog? Convert the bar to milligrams of theobromine, compare it with Merck's 20, 40 and 60 mg/kg thresholds, and see when signs usually start.

What It Is

Chocolate is made from cacao beans, which contain two methylxanthines: theobromine and, in smaller amounts, caffeine. Dogs clear theobromine very slowly, so a dose that would be harmless to a person stays in a dog's blood for many hours and keeps stimulating the heart and nervous system. The darker and less sweet the product, the more theobromine it carries per gram.

Where Pets Come Across It

Most cases happen around holidays: Easter eggs, Advent calendars, Halloween bags and Christmas tins left on low tables or wrapped under the tree. Baking chocolate, cocoa powder, chocolate-covered espresso beans and brownie mix are the riskiest because they are so concentrated. Cocoa-bean-hull garden mulch can also contain methylxanthines.

Which Animals Are Affected

Dogs are by far the most common patients because they will eat a whole bar, wrapper and all. Cats are just as sensitive per kilogram but rarely eat enough. Birds, rabbits and ferrets are also susceptible, and their small size means a single square can matter.

Published Toxic Dose

The Merck Veterinary Manual gives these thresholds for dogs: mild signs such as vomiting, diarrhoea and thirst from about 20 mg/kg of methylxanthines, effects on the heart at 40–50 mg/kg, and seizures at 60 mg/kg or more. Merck's table lists roughly 2.3 mg per gram in milk chocolate, 5.3–5.6 mg/g in semisweet and dark chocolate, about 15.5 mg/g in unsweetened baking chocolate and about 28 mg/g in dry cocoa powder. White chocolate has almost none. Individual dogs vary, so treat these as guides rather than safe limits.

Signs and How Soon They Appear

Signs usually start 6 to 12 hours after eating. Expect restlessness, panting, vomiting, diarrhoea, drinking and urinating more, and a racing heart. Larger doses bring tremors, high body temperature, abnormal heart rhythm and seizures. Because theobromine lasts so long in dogs, signs can continue for a day or more, and the fat and sugar in chocolate can also trigger pancreatitis a few days later.

What to Do Right Now

Work out the product type and how much is missing from the packet, then call your vet or a pet poison line with your dog's weight. Bring the wrapper to the clinic. Do not try to make your dog vomit with salt or hydrogen peroxide at home; your vet can do this safely if it is still worthwhile.

Frequently Asked Questions

Sources and References

• Merck Veterinary Manual: Chocolate Toxicosis in Animals
• Pet Poison Helpline: Chocolate

Related Poisons