Theobromine is the main reason that people know dogs can't always eat food that people can eat. Theobromine is from several plants but the main think that it's in is cacao. It's one of those wonderful ingredients that makes chocolate yummy. Now many people know that chocolate kills dogs, but really it takes about* 100mg/kg to cause toxicity in a dog. We get calls all the time regarding dogs that ate Valentines or Halloween candy. We always advise the owners to either make the DOG vomit (give them about 2 tbsp give them about 10 minutes, repeat (only up to 6 or so tablespoons, and only if the dog is more than 10 lbs) if needed. NEVER INDUCE VOMITING IN A CAT! (They tend to continue to vomit, and eventually get ulcers because of the vomiting.) Honestly when we use H2O2 it is more labor intensive. I tend the either run around with the dog, or shake their tummy around so that it is quicker (and easier) for them to vomit. If it is already in the dog's system, and it is too late to get them to vomit, the things that it will likely cause are digestive problems, then if the dog ate too much for it's poor body it can cause excess drinking and urination. Then it causes nervous system and cardiovascular system problems. It can cause muscle spasms, seizures, increase heart rate, coma and death. It's a lot like caffeine, so you can somewhat understand how all this happens. Some people will also call and ask about things like chocolate cookies, and that's a whole new concern.
Foods that are high in fat content can cause dogs to suffer from acute pancreatitis. We worry more about the butter in those cookies than those little chocolate chips. Pancreatitis causes dogs to have tummy trouble, dehydration, not eat or drink, act lethargic, and sometimes to have a painful abdomen. If they end up with pancreatitis they need to see a doctor. They stay on intravenous fluids until they perk up and act more normal, and their blood values go back to normal, which usually takes several days.
Stick with doggie food and treats!
Part of why I wanted to make this note is because I met a doggie named Niko :) And I'm hoping that maybe I'll take up writing occasionally again.
*-http://en.wikipedia.org/wiki/Theobromine_poisoning Wikipedia has a good chart on toxicity information.