Chocolate contains theobromine and caffeine, compounds that dogs metabolise far more slowly than humans, so ingestion can cause vomiting, tremors, seizures and in severe cases be fatal.
Why chocolate is toxic
The toxic components in chocolate are methylxanthines, chiefly theobromine and to a lesser extent caffeine; dogs clear these substances much more slowly than people, allowing toxic levels to build and affect the heart and nervous system.
Types of chocolate and relative risk
Different chocolates contain very different concentrations of theobromine: dark chocolate, baking chocolate and cocoa powder are far more dangerous per gram than milk chocolate, so smaller amounts of dark varieties can cause severe poisoning.
Signs and symptoms
Early signs include vomiting, diarrhoea and restlessness followed by increased heart rate, muscle tremors and seizures in more serious cases; severe intoxication can lead to cardiac arrhythmias, hyperthermia and death if not treated promptly.
What to do if ingestion occurs
If a dog has eaten chocolate, contact a veterinarian or a poison‑control service immediately; treatment may include inducing vomiting, administering activated charcoal to limit absorption, intravenous fluids and medications to control heart rate, seizures and other complications.
Prevention and takeaway
Keep all chocolate, cocoa products and cocoa‑containing items out of pets’ reach, be aware of hazards like cocoa bark mulch and educate household members and visitors about the risk; rapid veterinary care greatly improves outcomes when exposure happens.