You've heard the warnings- "don't give your dog chocolate, it's poison." But you've also got that friend who says "Oh my dog eats chocolate all the time." So what's the deal?
The truth is, chocolate poisoning occurs differently in different dogs and varies according to the size of the dog, his temperment and the kind of chocolate consumed. The toxic substance in chocolate is theobromine, a caffein like substance that can be toxic to humans in large quantities as well. Chocolate also contains caffein which is also toxic to dogs.
Both of these substances are addicting and intoxicating to dogs. Chocolate is doggie crack. It tastes good, it smells divine, it gets them stoned and they will always want more. It increases neurological activity, raises their heart rate and makes them hyper and hyper sensitive. This "high" just like people highs, is a mild poisoning. A dog under the influence of chocolate is more difficult to control and more likely to bite if presented with an uncomfortable situation. Just like people on drugs. Of course dogs (like some people) have no sense of when enough is enough. If some is good, more must be better and overdoses are not uncommon. How much is too much chocolate? 125-250 mgs/kg of theobromine per pound of bodyweight will kill a dog. 50 mgs per pound will cause a toxic reaction. Less may, depending on the dog.
Different types of chocolate have different theobromine levels. While your average sized dog can probably eat a full sized milk chocolate candy bar, a cocoa bean or two will make him very sick. Milk chocolate contains about 50 mgs of theobromine per ounce while unsweetened baking chocolate contains 500 mgs per ounce. Cocoa powder, about 800 mgs per ounce and cocoa beans, about a thousand. So, while a "fun sized" Snickers bar isn't likely to kill your dog, no matter how small it is, (at less than 20mgs it still might make a teacup yorkie sick) a full sized Hershey's Special Dark at almost 1500 mgs will kill a yorkie, chuhuahua or pomeranian outright and could even make a 50 pounder pretty ill or at the very least, stoned. But don't take this as a guideline. Remember, 125-250 per pound is the lethal dose in a healthy dog and 50 mgs per pound will make him quite ill. A dog that's already high strung or has heart problems could die from a much lower dose.
After your dog eats chocolate, the first thing you'll notice is that he is hyper and difficult to control. He might roll around on the ground more than usual and disregard your commands more than usual. He might lay down and get back up again, walk around in urgent circles and bark at nothing more often than usual. He is also more likely to get irritable and growl and bite. Or worse, bite without growling. This "high" can last for 48 hours.
If he is overdosing, he may or may not be more thirsty than normal. His urination will increase and he may have diarrhea and vomiting. Basically, he will act like he is feeling like you felt after you drank two pots of coffee in an effort to finish your final paper in college and a third pot to get through class the next day and smoked two packs of cigarettes in the process. (Some of you get sick thinking about it, some of you can handle it just fine. Remember that dogs differ this way too.) This can progress to cardiac arrhythmias and seizures.
If you catch your dog eating chocolate, you should induce vomiting (with syrup of Ipecac) and give him lots of water (Sweeten it with some chicken broth to encourage him to drink it.) , some charcoal tablets and call your vet. Depending on the amount, your vet may tell you to just watch him or ask you to bring him in.
If your dog shows signs of chocolate poisoning, but you didn't catch him eating chocolate and thus have no way of knowing how much he ate, take him to the vet right away. Once toxic symptoms show up (diarrhea, vomiting, arrhythmia, etc.) it's out of your hands and in the vet's.
A final warning. There are more sources of theobromine than candy. Cocoa mulch is popular in some locations because it has a great texture and smells fabulous. Keeping your dog securely in your own yard and, if you use cocoa mulch, away from your gardens will prevent him from ever coming in contact with the stuff, but it's good to be aware it's out there.