My dog ate chocolate, so why isn’t he sick?

“My dog ate chocolate.”  These are the most common words every toxicologist hears.

I know I said I wouldn’t write about chocolate because the vast majority of pet owners were already aware of the dangers in giving it to their pets.  That was before I found an awesome online chocolate calculator available to the general public that estimated your dog’s risk level based on dose and the type of chocolate!

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Seeing as Easter is knocking on the front door, I gave into pressure and decided to write an article about chocolate poisoning.  But I want to teach you something you didn’t know, so be prepared for an extremely detailed look at chocolate, why it is toxic, why some forms are more toxic than others, and how we determine dose.

My dog ate chocolate….

Despite the fact that pet owners are aware of the risks it poses to their companions, chocolate is still one of the most common exposures that occur.  Whether obtained during the holiday, during a time when someone was baking, or rummaged out of someone’s purse, there are thousands of different products that contain or are made from chocolate.

Due to a cat’s inability to taste ‘sweet’ the way we do, dogs are by far the main culprit in these chocolate shenanigans.   Unfortunately, many people have grown lax about keeping an eye on their candy.  In many cases, this is due to witnessing a previous exposure that resulted in a lack of signs.  I cannot count the number of times I have heard, “Chocolate is not that bad.  My dog ate chocolate once and didn’t even show any signs.  He must be resistant, so I don’t need to do anything now”.

The problem with that argument is that no two exposures are the same.  Frankly, no two chocolates are the same, so we can’t expect the same dog to react similarly with two different types of chocolate.  Let’s talk about why!

All chocolate starts with a bean.

We all have a general idea that cocoa beans make chocolate.  They grind them up or something, right?

Sort of.  The process for making chocolate is extremely interesting.  But, in interest of keeping it short and sweet, the beans are fermented, roasted, shelled, ground, then melted.  This melted substance is called “cocoa liquor”, (which contains no actual alcohol), and is the beginning of all chocolate.

Cocoa liquor is comprised of two separate parts: cocoa solids, (the non-fatty part of the bean), and cocoa butter, (the fatty part of the bean, which contains no actual cocoa powder, and no actual butter). Cocoa liquor contains about equal parts of butter and solids, (this varies a little).

Cocoa solids are essentially cocoa powder.  They contain the vast majority of the two ingredients that pose a problem to our pets: theobromine and caffeine, (both of which are chemical compounds called “methylxanthines” – these are stimulants.  This will become important later when we calculate chocolate content).

Cocoa butter (lacking both cocoa and butter) contains almost NO methylxanthines, and is mostly used as a fat substance in chocolate bars, or as a skin nutrient in beauty creams!

The toxicity of a certain type of chocolate is classified by total methylxanthine content, (which is a combination of the amount of theobromine and the amount of caffeine), per ounce.

Is your brain broken yet?  I hope not, because now we’re going to talk about they types of chocolate with which we are more familiar! (You can find reference numbers for doses here).

Cocoa powder – This is essentially pure cocoa solids, (and contains all of the bad chemicals for our pets).  Because cocoa powder has had the cocoa butter removed, it is an extremely concentrated form of chocolate.  Cocoa powder contains 700-800 milligrams of total methlyxanthines (theobromine and caffeine) per ounce.

Unsweetened Baker’s Chocolate – This is either formed from the chocolate liquor plus a little bit of extra fat, or the solids are added to a different source of fat than the cocoa butter (this is a manufacturer preference), and mixed into at least a 50% cocoa and 50% fat mixture. Because baker’s chocolate still contains fat, it is NOT as concentrated as cocoa powder.  Sitting at about 50% solids, baker’s chocolate only contains about 50% of the total chemical content that cocoa powder does.  It contains roughly 400-450 milligrams of total methylxanthines per ounce.

Dark chocolate – Dark chocolate is made either by adding sugar and fat to baker’s chocolate (thus diluting it further), or by adding sugar and fat to cocoa powder.  Dark chocolate is tricky, because there is no “standard” amount of chocolate solids used by any one manufacturer. You can see dark chocolate come in ranges from about 60% dark chocolate to 90% dark chocolate. This makes it a bit more complicated to calculate.  We work our calculations from the total methylxanthine content in baker’s chocolate, or 400 mg/oz. (Baker’s chocolate being a “99% dark chocolate, or 99% cacao”).

• 80% dark chocolate (like the one pictured left) contains 80% of 400 milligrams (0.8 * 400) or 320 milligrams of total methylxanthines per ounce.
• A lesser concentrated dark chocolate at 50% cacao contains (0.5 * 400) 200 milligrams of total methylxanthines per ounce.
• The average consumable dark chocolate bar contains more sugar and fat than it does cocoa, and generally sits around 40% cacao, or 165 milligrams of total methlyxanthines per ounce.

Semi-sweet chocolate – For all you bakers out there, this is where your chocolate chips come in.  While they are dark chocolate, they are usually highly sweetened, so they taste good in your cookies.  They contain about the same amount as your average consumable dark chocolate bar, and weight in at roughly 165 milligrams of total methlyxanthines per ounce.

Milk chocolate – This is by far and large the most common form of chocolate on the market.  We LOVE our milk chocolate.  Luckily, it is also one of the lesser concentrated forms of chocolate.  Milk chocolate is like dark chocolate with more fat, more sugar, and added milk for the creamy texture.  All of that other content dilutes our cocoa solids even further, reducing the amount in milk chocolate to about 65 milligrams of total methylxanthine content per ounce.

White chocolate – White chocolate isn’t really “chocolate” at all.  It is made by adding fats and sugars to cocoa butter.  Because cocoa butter contains virtually no methylxanthines, white chocolate contains about 1 milligram of total methylxathines per ounce.

Whew!  But now what?  My dog ate chocolate, and these numbers don’t mean anything to me!

Don’t fret, I have you covered.  The calculator up top will automatically calculate the risk level for you automatically, but let’s talk about how those calculations are done.

Some over-simplified math

All doses for any exposure are calculated in milligrams of toxin per kilogram of the animals’ body-weight.  For chocolate, we have that extra step in trying to determine how many milligrams of toxin are in each ounce of chocolate, but after we have that figured out, the rest is all the same:

{Millgrams of total methylxanthines per ounce x the number of ounces of chocolate ingested} / pet’s weight in kilograms = dose.

For example, if your 10 pound (4.5 kg) dog ate a standard 1.5 ounce Hershey’s milk chocolate bar:

{65 milligrams of total methylxanthines per ounce of milk chocolate x 1.5 ounces ingested} / 4.5 kilograms = 21.67 milligrams of total methylxanthines per kilogram of dog.

It all boils down to dose.

Once the dose is known, we can assess the risk level of your dog.  The larger the dog, the smaller the dose will be, and the less risk they will be at.  Cat-lovers, I see you here too!  Even though I’ve mainly been talking about dogs, the risk levels for cats and chocolate is about the same as it is for dogs and chocolate.

So what are the risks? All vets will assess this differently based on the individual health of your dog, your dog’s age, the type of chocolate, medications your animal is taking, etc.  (Meaning there is no hard-and fast rule.  ALWAYS contact your vet if your dog eats chocolate). But as a rough guideline:

Up to 20 milligrams per kilogram is lower-risk.  We may still see vomiting, diarrhea, and increased thirst.

Between 20-40 milligrams per kilogram is of moderate risk.  We start to see signs of stimulation, and pets become hyperactive, anxious, and may pace and pant.

Anything over 40 milligrams per kilogram is of high risk.  At this point, we start to see the heart become involved with rapid heart rate, heart rhythm abnormalities, premature heart beats, and potentially can lead to heart failure.

Anything over 60 milligrams per kilogram will cause advanced signs of stimulation, including muscle tremors and seizures.

Due to the high fat and sugar content in chocolate, animals who ingest it also have the possibility of developing pancreatitis within 2-3 days, as they are not able to break down fats and sugars as easily as we are.

But why can I eat chocolate, and my dog or cat cannot?

Mostly, it has to do with how quickly we metabolize the chemicals in chocolate.  When we put chocolate into our tummies, our bodies very quickly and efficiently break it down and eliminate it. We still see some of the milder stimulation effects of chocolate, much like you would if you drank a cup of coffee.

The same is not true for our pets.  Their bodies are not efficient at breaking down these chemicals, so the more they eat, the more it builds up in their systems, and the more stimulated they get.  Signs of stimulation in a dog or cat may even last up to 72 hours.

Because of the huge variance in types of chocolate, one dog is not likely to react the same way to a second exposure as he may have to the first.  Just because your 100 pound dog didn’t die from eating a few chocolate chips on the floor, it doesn’t mean he won’t have some serious problems if he licks up a few tablespoons of cocoa powder, or gets a bite of baker’s chocolate. This means you always need to contact your vet or poison control if your dog happens to get into chocolate.