Adobe Animal Hospital, Los Altos, CA

Cocoa Mulch, which is sold by Home Depot, Foreman's Garden Supply, Target and other Garden supply stores, can contain a lethal ingredient called "Theobromine". Theobromine is the ingredient that is used to make all chocolate, especially dark or baker's chocolate which is toxic to dogs.

Cocoa bean shells contain potentially toxic quantities of theobromine, a xanthine compound similar in effects to caffeine and theophylline.

Veterinarians have noted that cocoa mulch contains ingredients that could pose a health risk to dogs (and other pets that might be tempted to ingest it): "Cocoa mulch is a risk, especially to dogs," said Dr. Larry Family of Aqueduct Animal Hospital. Found in most home garden centers, cocoa mulch is known for its fine texture and the sweet smell the fresh mulch gives off. But getting past the scent, Family says cocoa mulch can be dangerous if a dog starts eating it. It contains two key ingredients found in chocolate: theobromine and caffeine. Similar to eating chocolate, he says a dog that eats just a few ounces of cocoa mulch could starting having stomach problems and it could get worse if it eats more. "As time goes on they might act restless, excited, it can produce tremors and seriously seizures," Family explained. "Puppies are very curious animals. So they're going to be attracted to various things around the yard and the effect of eating cocoa mulch seems to be more severe in the small breeds, and it depends on the amount they actually ingest," Family said.

The American Society for the Prevention of Cruelty to Animals (ASPCA) confirms the potential effects of theobromine and caffeine on dogs:

Eaten by a 50-pound dog, about 2 ounces of cocoa bean mulch may cause gastrointestinal upset; about 4.5 ounces, increased heart rate; about 5.3 ounces, seizures; and over 9 ounces, death. (In contrast, a 50-pound dog can eat up to about 7.5 ounces of milk chocolate without gastrointestinal upset and up to about a pound of milk chocolate without increased heart rate.) According to tables we've examined, cocoa mulch contains 300-1200 mg. of theobromine per ounce, making cocoa mulch one of the strongest concentrations of theobromine a pet is likely to encounter in any chocolate product.

Responsible pet owners should take care in their selection of cocoa mulch brands; some might prefer to choose another form of soil enhancement for their gardens, such as cedar-based products, rather than gamble their dogs won't be attracted to or harmed by cocoa mulch.

The danger of canine theobromine poisoning does not begin and end with cocoa mulch, however: chocolate in any form poses substantial risks to some pets. This most beloved of foodstuffs contains theobromine and small amounts of caffeine, both of which can sicken and even kill cats and dogs. Chocolate's toxicity to animals is directly related to three factors: the type of chocolate, the size of the animal, and the amount of chocolate ingested. Unsweetened baking chocolate presents the greatest danger to pets because it contains the highest amount of theobromine, approximately 390-450 mg. per ounce. White chocolate contains the least. As a general rule of thumb, one ounce of milk chocolate per pound of body weight can be lethal for dogs and cats. (Milk chocolate contains approximately 44-66 mg of theobromine per ounce.)

Theobromine affects the heart, central nervous system, and kidneys, causing nausea and vomiting, restlessness, diarrhea, muscle tremors, and increased urination. Cardiac arrhythmia and seizures are symptoms of more advanced poisoning. Other than induced vomiting, vets have no treatment or antidote for theobromine poisoning. Death can occur in 12 to 24 hours. This type of poisoning is uncommon because it is rare that a dog, even a small dog, will eat enough chocolate to cause anything more than an upset stomach. Yet it can happen, especially if the animal gets into baking chocolate or powdered cocoa, two forms of the sweet particularly loaded with theobromine.

Do not feed chocolate to dogs or cats. If your animal begins exhibiting signs of distress and you believe he might have gotten into some chocolate, call your veterinarian immediately. (It will help if you can supply information about the approximate weight of your critter, what sort of chocolate was ingested ? white, milk, dark, cocoa powder, baking ? and roughly how much.) But time is of the essence if such a poisoning has indeed taken place, so make the call right away.