Chocolate Poisoning

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One of the most memorable cases that I saw in my final year at vet school, was a two year old bitch called Cleo, who was an emergency admission one April. Her owners had come downstairs one morning just before Easter, to find her collapsed in the kitchen, barely able to breath, and surrounded by pools of bloody vomit. She was taken to her local vet immediately, who referred her on to the specialists at the vet school. Cleo was hospitalised as soon as she arrived and intensive care instigated, whilst a whole battery of tests were performed. As the results came back, everyone involved with the case looked more and more perplexed - there were plenty of abnormalities in her test results, but we were struggling to reach a diagnosis.

Fortunately for Cleo, on returning home, her owners had discovered the remnants of a Thornton’s Luxury Easter Egg hidden behind the sofa in their lounge. I say ‘remnants’, but all that was actually left was a brightly coloured ribbon and some cellophane! During the night, Cleo had found the egg, and over-indulged in a midnight feast, and now she had chocolate poisoning.

Every year there are hundreds of telephone enquires to the Veterinary Poisons Information Service, concerning the ingestion of chocolate by dogs. These enquires are relatively evenly spread throughout the year, but reach a peak around Easter and Christmas. The cause of the poisoning is theobromine, found in the cocoa solids from which chocolate is made, as well as in cocoa powder, cocoa beans and more recently some garden mulches. As little as 100mg theobromine per kg of your pet dog can be fatal. Put another way, the chart below shows approximately how much of various cocoa products could be fatal to two common breeds. The figures are approximate, based on a standard breed weight, and a standard amount of cocoa solids in the chocolate products, but even as a first approximation, make startling reading:

  Jack Russel Terrier Labrador
White Chocolate > 55 kg (!) > 277 kg (!)
Milk Chocolate 227g 1.1kg
Plain Chocolate 32g


Coco Powder 19g 96g
Cocoa shell mulches 17g 83g

Fortunately we don’t see too many cases of chocolate poisoning, but the problem arises since the symptoms which it produces mimic so many other things and don’t occur for at least 4 – 24 hours after ingestion. Typically, we see vomiting, including blood, excessive drinking, hyperactivity, inco-ordination and a racing heart. In severe cases these signs may be accompanied by muscle rigidity, panting, fever, convulsions and heart arrhythmias, and may ultimately lead to kidney or heart failure.

There is no antidote for theobromine poisoning and treatment is necessary for any amount ingested. Typically, we will induce vomiting to slow down the rate of chocolate absorption from the gut, pump out the stomach and feed activated charcoal which will absorb any theobromine left in the gut. Fitting or convulsing animals are sedated, and careful monitoring of the heart and pulse is undertaken. If necessary, certain medications can be used to regulate the heart’s rhythm, but not without the risk of side-effects, so such drugs are reserved for life-threatening cases only.

It is important to stress that with prompt intervention in potentially serious cases, the prognosis for a poisoned dog is usually good. Fatal cases are thankfully rare, and in general it is cocoa-bean mulch cases which cause death, rather than those caused by stolen chocolate!

And what happened to Cleo?

Well, it took eight days of intensive care, round the clock heart monitoring, and every day the owners debated whether or not to put her to sleep, but on the eighth day she suddenly perked up and never looked back. She went home shortly afterwards – to a house where all Easter eggs were safely shut away in cupboards.

There was only one fact that I omitted from the story, and that was what type of dog Cleo was……

A chocolate Labrador – honest!