My active young dog burst into the room and, seeing us eating, immediately checked herself and lay down. To reward this show of self-control, I tossed a piece of my candy her way.
"You can't do that!" gasped a friend. "You'll poison her! That's chocolate!"
But I knew that a single M&M® wouldn't do her any harm. Could it? What are the risks of chocolate, a commonly recognized danger to dogs?
photo by AntaresArt.com
Why is chocolate lethal to dogs?
Chocolate is not dangerous to humans—fortunately for aficionados like myself. It has a long and wonderful history, serving as legal tender, supposed aphrodisiac, emergency rations, and sweet treat. Chocolate is made from the seed of the cacao tree. Interestingly, these trees cannot reproduce without the aid of hungry wildlife; animals must break open the pod to release the seeds. The fruit itself is sweet, but animals disdain the bitter seeds and discard them, thereby planting new cacao trees. It is from the seeds that we obtain cacao.
Cacao can be processed into a variety of products. Hulled, ground cacao beans yield a liquid, called chocolate liquor, which contains no alcohol. When the fat from cacao (cocoa butter) is removed, cocoa powder remains.
From these elements, the chocolate we know and love is manufactured in several forms. Baking chocolate is 50-60% cocoa butter, and unsweetened. Semisweet chocolate is 35% chocolate liquor, and milk chocolate is 10% chocolate liquor, the remainder of each of these chocolates made up of milk products, vanilla, lecithin, and/or fillers. (Note that "white chocolate" hardly deserves the name, containing only 20% cocoa butter.) These standards vary by country.
All of these variations contain what was present in the original cacao seed—theobromine and caffeine—the roots of chocolate toxicity, but not the only culprits.
Other varieties of "chocolate poisoning"
The simplest and perhaps most common form of chocolate poisoning isn't really poisoning at all. When we mix chocolate into cakes, puddings, drinks, and other treats, we usually add lots of fat and sugar, too. When a dog steals one of these treats, the chocolate content is usually low enough to avoid real toxicity, but the other ingredients can make the dog ill. The resulting stomach upset is unpleasant, but rarely dangerous.
A more worrisome event occurs when a dog eats too much processed fat and develops pancreatitis. Symptoms include vomiting, diarrhea, and abdominal pain. This illness is potentially lethal and requires treatment, but it is not caused by chocolate itself.
The theobromine in chocolate is inherently toxic to dogs and cats. It is a natural stimulant and can adversely affect the nervous system and the heart. An affected dog may show increased blood pressure, increased (or occasionally slowed) heart rate, cardiac dysrhythmia, tremors, seizures, panting, urinary incontinence, and, finally, coma and death. Definitely not something to mess with!
Many pet owners do not realize the serious risk of theobromine poisoning, and often they assume that once a dog has vomited after ingesting chocolate, the risk is lessened. But, because of its texture, chocolate does not regurgitate well (so to speak), and only a portion of the chocolate is vomited up. Veterinary protocol recommends an emetic, but does warn that the emetic will not clear the dog's system on its own.
It is important to know that symptoms of theobromine poisoning may take up to 24 hours to develop, even after the dog has vomited. Theobromine has a half-life of 17.5 hours, which means that it may take several days to clear the system. So while a single helping of chocolate may not be enough to endanger an animal, several small doses can have a disastrous cumulative effect.
Caffeine is another natural stimulant present in cacao. It has many of the same effects as theobromine, and the presence of both in chocolate products can be a double blow to animals. The effects of caffeine can be seen as the following symptoms: rapid heartbeat, hyper-excitability, fever, tremors, seizures, and irregular heartbeat. Dilation of blood vessels may cause hemorrhaging.
If your pet finds and ingests chocolate without your knowledge, his life may depend on your early recognition of the symptoms. The first symptom will be abdominal pain and vomiting; the vomit will usually smell of chocolate (and may contain blood). The stimulants will make the dog restless or nervous, and he may show difficulty in movement. Drooling is not uncommon.
Later symptoms include rapid breathing and muscle tremors, which eventually become convulsions. Because caffeine is also a diuretic, the dog may pass more urine than usual (which may contain blood) or may be more thirsty.
Keep an affected dog calm; his rapid or irregular heartbeat is more susceptible to the strain of exercise.
Both theobromine and caffeine have a lethal dose as low as 100 mg per kilogram of body weight, but symptoms may appear after as little as 20 mg/kg (about 9 mg per pound of body weight). Treatment is recommended when the combined methylxanthine dosage—both theobromine and caffeine together—is 20 mg/kg.
If you suspect your dog or cat has ingested chocolate (or anything containing theobromine or caffeine), do not wait for symptoms! Contact your veterinarian immediately, as time is of the essence. Remember, symptoms may take up to 24 hours to develop (though usually they appear within a few hours), and quick removal of the poison is the best hope for recovery.
There is no antidote for theobromine or caffeine poisoning. The best treatment is to support the victim as the toxin is processed through the system. Drugs may be administered to control convulsions, heart rate, and abnormal heart rhythms, and the stomach may be purged to remove as much toxin as possible. Activated charcoal can help reduce the half-life of theobromine in the system, preventing internal reabsorption. A dog with vomiting or diarrhea may need intravenous fluids to prevent dehydration. Catheters are recommended, as both theobromine and caffeine may be reabsorbed through the bladder. Acute cases may require that the animal be hospitalized for several days. All of this support and care should be done at the direction, and under the supervision, of your vet.
It has been suggested that a dog should never taste chocolate, lest he be more likely to eat it later, but it is dangerous to imply that a dog who has not tasted chocolate will not eat it if it is available! To assume that a dog that has never tasted chocolate won't be tempted by it at some point is not realistic; in fact, it's similar to the myth that feeding a dog table scraps will cause him to crave human food, while a dog that has not had scraps will be content with dry kibble. Dogs are opportunists and will rarely turn down anything sweet, fattening, or tasty.
This is not to say that, because they will eat it anyway, we should allow our pets to eat chocolate or scraps indiscriminately. Even small doses of dangerous foods can have a cumulative effect. It is important to remember that there are sources of danger other than chocolate, as well—dogs have died after ingesting herbal weight loss supplements containing caffeine, for example. Common sense dictates that we keep medications safely out of reach, but remember to do the same with "all-natural" products as well!
Beware of "safe chocolate" treats marketed for dogs. These products still contain cocoa powder, and while they shouldn't cause any ill effect in the small servings recommended, a dog that helped himself to the container could still get into trouble.
While my single M&M as a handy reward for good behavior was not likely to cause problems, it could be a dangerous habit to develop. Keep the chocolate candy and caffeinated beverages for yourself; there are better treats to share with your pet.
How much is too much?
Listed below are the quantities of theobromine and caffeine in several common forms of chocolate.
|Instant Cocoa Powder
Product definitions vary by country, and qualities vary widely within categories. Dark chocolate may contain only 35% chocolate liquor or as much as 70%! When in doubt, call your vet.
Milk chocolate contains approximately 50 mg/oz of theobromine and 6 mg/oz of caffeine, or 896 mg of methylxanthine per pound. A 50-pound dog might start to show symptoms after ingesting 450 mg (9 mg/lb), or about half a pound of milk chocolate; higher doses could be lethal. Remember, treatment is recommended if the combined dose reaches 20 mg/kg (9 mg/pound of body weight), even if the individual doses are less.
Source: Roger W. Gfeller and Shawn P. Messonnier, Handbook of Small Animal Toxicology and Poisonings, 2nd Edition (Mosby, 2003).