When I was little, my mother taught me to share with my friends. When I was a little older, I was told that doesn't apply when it comes to chocolate and dogs.

I've heard it many times since - it seems to be common knowledge that dogs are allergic to chocolate, and that it can kill them. But is that really true?

Well firstly, its not an allergy. Chocolate contains a compound called theobromine, which in sufficient quantities, is toxic to dogs.

What is theobromine?

Theobromine comes from the cacao plant, and is found in chocolate. It can also be found in tea leaves, and is similar to caffeine.

In humans, it can be used as a vasodilator, diuretic, or heart stimulant. That means it can widen the blood vessels, help you to pee, or speed up your heart. In large quantities it can work as a poison, but you'll rarely consume enough for this to happen.

Some animals, such as dogs, have a stronger reaction. It can cause dehydration, problems with digestion, and it slows the heart. Theobromine can be fatal, causing seizures and death.

Does this mean my dog can die from a single M&M?

Well, not really. It's not good for dogs, but it will take more than that to be fatal.

It takes between 100-150 mg per kg to cause a toxic reaction. As little as 50 grams of chocolate can poison a smaller dog, or 400 grams for an average sized dog.

Milk chocolate contains the lowest concentration of theobromine, and baker's chocolate holds a much higher concentration. So be extra careful to keep your dog away from baked chocolate sweets.

Dogs can develop a taste for it - they actually find the flavor addictive. So avoid letting your dog eat even a small amount, or your pet might try to seek out more.

Is it treatable?

If caught early, theobromine poisoning can be treatable. Early symptoms include vomiting, diarrhea, and excessive thirst.

There is no specific antidote for theobromine poisoning, but your vet will probably start out by causing your dog to vomit. If your dog is experiencing seizures, a general anaesthesia may be required.

Your dog will likely need an IV for fluids, and your vet may need to treat with intestinal absorbents to absorb the theobromine.

If you suspect your dog has eaten chocolate, you should consult with your vet who can advise you on the specific treatment he or she recommends.