Chocolate is poisonous to dogs
However, the hazard of chocolate to your dog depends on the type of chocolate, the amount consumed and your dog's size. In large enough amounts, chocolate and cocoa products can kill your dog.

Why not chocolate?
The toxic component of chocolate is theobromine. Humans easily metabolize theobromine, but dogs process it much more slowly, allowing it to build up to toxic levels in their system.
A large dog can consume more chocolate than a small dog before suffering ill effects.
A small amount of chocolate will probably only give your dog an upset stomach with vomiting or diarrhea.
With large amounts, theobromine can produce muscle tremors, seizures, an irregular heartbeat, internal bleeding or a heart attack. The onset of theobromine poisoning is usually marked by severe hyperactivity.

Why is Chocolate Lethal?
Chocolate contains theobromine. A naturally occurring stimulant found in the cocoa bean, theobromine increases urination and affects the central nervous system as well as heart muscle. While amounts vary by type of chocolate, it's the theobromine that is poisonous to dogs.

Symptoms of Chocolate Dog Ingestion and Poisoning
You can recognize that your dog has eaten a toxic dose of chocolate from the symptoms. Within the first few hours, the evidence includes vomiting, diarrhea or hyperactivity. As time passes and there's increased absorption of the toxic substance, you'll see an increase in the dog's heart rate, which can cause arrhythmia, restlessness, hyperactivity, muscle twitching, increased urination or excessive panting.
This can lead to hyperthermia, muscle tremors, seizures, coma and even death.



How Much Chocolate Is Deadly?
If a 50-pound dog eats a teaspoonful of milk chocolate, it's not going to cause serious problems. However, if that same dog gorges himself on a two-layer chocolate cake, his stomach will feel more than upset and soon it's likely he'll be vomiting or experiencing diarrhea.
To answer the question "How much is too much" is not simple. The health and age of your dog must be considered. Obviously if your dog is aged and not in top shape, his reaction to a plate of chocolate is going to be different from a young healthy dog of the same weight.
Another fact that must be considered is this: Not all chocolate is the same. Some has a small amount of theobromine; another type has a large amount and still another contains an amount that is somewhere in between. The quantity has a relationship with the weight of your dog. Small dogs can be poisoned, it is easy to understand, from smaller amounts of theobromine than large dogs.
Which chocolate is the safest, relatively speaking? White chocolate. It has the least amount of theobromine: 1 mg per ounce. Far on the other side of the spectrum is baking chocolate, which has a huge 450 mg of theobromine per ounce!
Here are a few other chocolates for you to ponder: hot chocolate, 12 mg of theobromine per ounce; milk chocolate, 60 mg/oz; and up there near baking chocolate: semi-sweet chocolate with 260 mg/oz.

Knowing which chocolate is the most toxic is important, but leaves one wondering how much must be eaten to poison a dog. The list in this box should be helpful. Maybe you can clip it and post it on your refrigerator? 

White chocolate:200 ounces per pound of body weight. It takes 250 pounds of white chocolate to cause signs of poisoning in a 20-pound dog, 125 pounds for a 10-pound dog.

Milk chocolate:1 ounce per pound of body weight. Approximately one pound of milk chocolate is poisonous to a 20-pound dog; one-half pound for a 10-pound dog. The average chocolate bar contains 2 to 3 ounces of milk chocolate. It would take 2-3 candy bars to poison a 10 pound dog. Semi-sweet chocolate has a similar toxic level.

Sweet cocoa:0.3 ounces per pound of body weight. One-third of a pound of sweet cocoa is toxic to a 20-pound dog; 1/6 pound for a 10-pound dog.

Baking chocolate: 0.1 ounce per pound body weight. Two one-ounce squares of bakers' chocolate is toxic to a 20-pound dog; one ounce for a 10-pound dog.

Treatment
The usual treatment for theobromine poisoning is to induce vomiting within two hours of ingestion. If you are worried or suspect that your dog may have eaten a large quantity of chocolate and they are showing any of the signs listed above, call your veterinarian immediately.

If you have a small dog that has eaten a box of chocolates, you need to call and go to your veterinarian right away. Do not wait.



Of course, never consider chocolate as a reward. Always provide healthy Treats or simply reward your dog with lots of love and attention.