Why is chocolate poisonous to dogs?

by Julie Harris


Many of us know or have read that chocolate is poisonous to dogs, cats, rabbits, and many other small animals, but what exactly makes it toxic and how does it affect their central nervous system which makes it so dangerous? To find this information I went in search of toxicology reports, looking for the WHY???

Chocolate at Christmas

Dogs have a different metabolism to humans. We know this because they sadly don’t live as long as us, with an average life span of 11 years. This plays a big part in how their bodies react to certain stimulates.

There is a group of ingredients called methylxanthines.


Methyi – xan- (zan) - thines

These include coffee beans, cocoa beans, tealeaves, caffeine and some medications.

The coca bean is a type of methylxanthine called Theobroma.


Although methylxanthines can be broken down easily in the human body it takes considerably longer to break down in dog’s bodies causing toxicity levels to build up over a few hours.

The toxicity of the chocolate depends on the size of the dog, whether it was eaten on a full or empty stomach, and the type of chocolate with dark chocolate being the most toxic and milk and white chocolate less so.

What happens when a dog eats chocolate?

We know the main toxic component in chocolate is Theobromine, which is a methylxanthine, and this in a dog’s system will cause cardiac and respiratory hyperactivity which means the heart becomes abnormally active. This can cause tremors and rapid breathing. Also the working of the stomach becomes more active and the dog experiences vomiting and diarrhoea. The overstimulation can also cause seizures and sometimes death.

These signs generally appear between 2-4 hours of ingestion but depending on a dog’s size could take as long as 12 hours.

Treatment is removal or neutralisation of the chocolate with activated charcoal which is known to absorb many poisons, plenty of fluids and control of the cardiac distress with medication.

In a study done between 2015 – 2019 in the UK, 156 dogs presented having eaten chocolate. Of the 156, 44 showed signs of toxicity with symptoms ranging from tremors and vomiting to cardiac distress. Of the 44 dogs all had digested dark chocolate, 43 of the 44 survived.

It’s important to understand that the toxic nature of chocolate can take up to 12 hours to cause distress to a dog so if you are aware that chocolate has been digested don’t become complaisant if the dog doesn’t show signs immediately. Be vigilant for many hours after, and always call your vet for advice. The cases of death after ingestion of chocolate are low, around 3% but not impossible, remember the darker the chocolate the more potential for toxicity and harm.

During this time of year when more chocolate is consumed, it is easy to leave it where a dog can reach. Make sure chocolate is packed away so cheeky 4-paws can’t help themselves.

 Dog at Christmas

Happy Christmas. Stay vigilant. Avoid a holiday vet visit.