Chocolate is highly toxic to dogs because it contains methylxanthines like theobromine and caffeine, which dogs cannot efficiently break down. Even small amounts can lead to gastrointestinal upset, hyperactivity, tremors, and in severe cases, coma or death. Toxicity depends on the dog's size, chocolate type (milk is less toxic than dark or unsweetened), and quantity consumed. For example, 1 ounce of milk chocolate per pound of body weight can be dangerous. If ingestion occurs, induce vomiting only under veterinary guidance and seek professional help promptly to mitigate risks. Prevention is key keep chocolate out of reach.