Visiting Vet: When chocolate isn’t sweet

Why it’s so important to keep those Hershey Kisses away from Fido.

If a dog finds a Valentine's Day candy wrapper, the chocolate may be toxic. — Tatiana Rodriguez

It all started with a small tropical tree indigenous to South and Central America, Theobroma cacao. This tree grows big red fruit pods. Inside the pods are seeds, also called beans. For more than 2,000 years, people have been making beverages from cacao. Theobroma means “food of the gods.” “Cacao” comes from the Olmec and Mayan words “kakaw” or “kakawa.”  But most of us call it chocolate, a word derived from the Aztec “xocoatl.” Whatever you call it, it’s delicious. Unfortunately, dogs think so too. Let’s talk about chocolate toxicity.

The first question is why can a person binge on chocolate with relative impunity while Kisses, the Cavalier King Charles Spaniel, can die from overindulging? Chocolate contains chemicals called methylxanthines, specifically theobromine and caffeine. When ingested, methylxanthines affect certain physiologic processes, resulting in stimulation of the heart and central nervous system. Hence the rush many people get from eating chocolate. The liver then metabolizes and clears the methylxanthines from the body. 

Theobromine is the substance primarily responsible for chocolate toxicosis, and dogs and people are affected differently by it. Toxicologists use a measurement called the LD50. That stands for Lethal Dose 50% and refers to the amount of a toxin that will kill half of the animals exposed at that level. It is usually expressed in milligrams per kilogram body weight. The human LD50 for theobromine is estimated around 1,000 mg/kg. An average weight person would need to eat 1,250 milk chocolate Hershey bars to reach the LD50. Since people tend to find the effects of chocolate pleasurable at low doses but unpleasant at higher levels, we usually get uncomfortably jittery and/or feel sick before we eat enough to make ourselves seriously ill. Our bodies also absorb, metabolize, and excrete theobromine quickly.

The LD50 in dogs is 250-500 mg/kg. In addition to having this much lower LD50, dogs also absorb, clear, and excrete theobromine much slower than humans do. And although some humans have been known to eat stupid, ridiculous amounts of chocolate, dogs are even more likely to gorge. All these things add up, making chocolate toxicosis a fairly common canine problem. Cats have a similar LD50 but aren’t particularly fond of chocolate and, as a species, are simply less prone to binge-eating. Chocolate toxicity has also been documented in wildlife. In New Hampshire in 2015 hunters put out 90 pounds of chocolate and chocolate donuts as bear bait. Several bears ingested it and died of heart failure due to the massive theobromine overdose. Even insects can be affected, with one study showing that hornets who had chocolate added to their diet became anxious and irritable (though I wonder exactly how they tested this!).

So if Kisses the Cavalier ate chocolate kisses, when do we worry? The risk depends on the size of dog and specific kind of chocolate, since different chocolate types contain different concentrations of theobromine. Cacao beans are first processed into a form called “cocoa mass” or “liquor” which can then be divided into cocoa butter and cocoa solids or powder. Cocoa butter is a fatty white substance containing virtually no theobromine. White chocolate is essentially just cocoa butter and thus poses no toxicity risk. Cocoa solids are solid, brown, bitter, and full of theobromine. Most chocolate products are a combination of both cocoa butter and cocoa solids in varying percentages. The higher the percentage of cocoa solids, the greater the amount of theobromine. 

Here’s the information your veterinarian would love to have: What kind of chocolate did Kisses eat? White, milk, semi-sweet, dark? What brand? How many ounces? If you have the wrappers, that’s helpful. Did it contain anything else that might be toxic to dogs such as raisins or xylitol sweetener? How long ago did Kisses eat it?  What is the maximum amount he may have eaten? If Kisses ate baked goods, do you have the recipe? How much cocoa powder was in it? In low doses, chocolate causes only mild problems — vomiting, diarrhea, excessive thirst, and excitability. In medium doses it starts to affect the heart, causing an elevated cardiac rate. In high doses, signs progress to tremors, seizures, cardiac arrhythmias, and, very rarely, respiratory failure and death.

The smaller the dog and the darker the chocolate, the greater the danger. To be on the safe side, we always base our treatment plan on the worst case scenario. The first step, when deemed necessary based on our calculations, is to induce emesis. That means we make Kisses vomit. This may be worth trying even six to eight hours post ingestion as chocolate tends to stay in the stomach a long time. Your veterinarian can explain how to do this at home, or may recommend an emergency visit as our medications may empty Kisses’ stomach more effectively than home methods. Then we reassess the dose. If Kisses upchucked most of the chocolate, we may relax and just treat him as an outpatient with fluids and medications for an upset tummy.  More serious chocolate exposures are best treated on an inpatient basis. There is no specific antidote so treatment involves repeated doses of activated charcoal to limit further absorption, intravenous fluid therapy, monitoring electrolytes, and administering medications to  treat tremors, anxiety, seizures, and cardiac arrhythmias as needed. 

Remember, it’s all about the math. If a huge Great Dane eats a single milk chocolate kiss, no treatment is necessary but, when in doubt, collect your information, then call your veterinarian or Animal Poison Control to calculate the theobromine dose. Don’t think because Kisses seems fine now, that everything is okay. Clinical signs may take up to 10 hours to appear (when it’s too late to “decontaminate”)  and persist for one to three days. That’s a long time for Kisses to spend in the hospital off-Island. Better still, keep all chocolate safely where only the humans can find and eat it. And, no, sadly, just because it starts out growing on a tree, you can’t count it as a vegetable. Sigh.