Chocolate is toxic for dogs
Chocolate contains methylxanthines (theobromine and caffeine), both of which are stimulants and toxic to dogs. Chocolate is also high in fat and this can cause pancreatitis. Dogs do not breakdown methylxanthines as well as humans and this allows it to build up. The higher the concentration of cocoa (i.e. the darker the chocolate), the more dangerous it is for dogs. Cocoa powder and bakers chocolate are the most toxic with milk chocolate and white chocolate being less toxic. Ingestion of 1 oz/kg of milk chocolate can cause symptoms. Ingestion of 2 oz/kg of milk chocolate or 0.2 oz/kg of bakers chocolate can cause death.
Symptoms can begin to appear in several hours and last up to 72 hours. If left untreated, it may lead to coma or death. You can try and induce vomiting within the first hour with 3% hydrogen peroxide. If your dog has ingested chocolate or any product containing chocolate (e.g. chocolate chip cookie, hot chocolate) and experiences the symptoms below, call your vet or pet poison hotline immediately.
Symptoms: vomiting, diarrhea, staggering, trouble with breathing, increased body temperature, seizures, muscle tremors, irregular heart beat, hyperactivity