Theobromine, found in chocolate, can be toxic to dogs. The toxic amount varies based on the type of chocolate and the size of the dog. Dark chocolate has higher theobromine levels. Generally, symptoms can appear with as little as 20mg of theobromine per kilogram of the dog’s body weight. For instance, mild symptoms could start at around 20mg/kg, but severe toxicity might occur at 40-50mg/kg. For example, a small dog of about 10 pounds could start showing signs of toxicity after consuming approximately 40-50 grams of dark chocolate. It’s crucial to contact a vet immediately if your dog consumes any chocolate.