Why is human chocolate is so bad for your pooch?

Ever wonder why chocolate is toxic to dogs? It all comes down to one molecule –  theobromine. It is a caffeinelike molecule that increases blood flow to the brain, is so hard for dogs to process that they can easily eat enough to be poisonous.

Dogs cannot metabolize the obromine and caffeine as well as humans can. The substances accumulate in the animal’s body in an amount that can be toxic or even fatal.  Also, if dogs should find chocolate, they tend to eat much more than a person would.

Few dogs eat fatal amounts of chocolate, but smaller doses can still cause seizures and other symptoms. Dark chocolate is worse than milk chocolate (it contains more theobromine), and smaller dogs are more easily affected.

What are the signs your dog has eaten chocolate?

One of the first signs to look for if you suspect your dog has eaten chocolate is restlessness and hyperactivity. Caffeine is absorbed ten times faster than theobromine, which takes up to ten hours to peak. Signs are usually seen two to four hours after eating the chocolate and can last up to 72 hours.

Both caffeine and theobromine cause elevated heart rate and blood pressure, and abnormal heart rhythms.

Vomiting, diarrhoea, muscle tremors/shaking and hyperthermia (high body temperature) can occur at toxic levels. Your dog might seek out cooler places, although will be unlikely to settle anywhere. The hyperthermia causes panting, the main way dogs lose body heat.

In more serious toxicity, it may cause muscle rigidity (stiffness), ataxia (uncoordinated movement), seizures and coma. Death results from problems with heart rhythm or failure of the respiratory system.

When combined, all of these biochemical changes stimulate the central nervous system and the heart muscle. Other types of muscles in the rest of the body called smooth muscles relax, which can cause respiratory problems and increased urination.

How much chocolate is fatal?

The toxic dose for theobromine is reported as 100-150mg per kg body weight, however occasionally problems are observed at doses as low as 20mg/kg. What this means in a practical sense, using 100mg/kg as a guide this equates to:

  • approximately 60 grams of milk chocolate per kg bodyweight
  • approximately 20 grams of semi-sweet chocolate per kg body weight
  • approximately 7 grams per kg body weight for baker’s chocolate per kg body weight

From this you can see that the toxic dose is dependant on the weight of the dog, and that unsweetened cooking chocolate is particularly dangerous. Take an 8 kg miniature poodle for example. 100 grams of milk chocolate is unlikely to cause more than a digestive upset, whereas just over half that much unsweetened cooking chocolate could have devastating effects.

I found this great Chocolate Toxicity calculator on Mosman Vet website HERE

Take-home message:
 • Chocolate is poisonous to dogs mostly because of its theobromine content, which dogs are unable to metabolize effectively. 
 •The amount of chocolate a dog can eat without showing symptoms varies drastically with their weight
 • If your dog eats chocolate, you should monitor them closely and seek veterinary attention if they show any symptoms, or if they are very young, pregnant or have other health concerns.

In the case of an accident or if you suspect your dog has eaten some chocolate, contact your vet immediately.