Theobromine, a chemical found in cocoa mulch, can be harmful to pets. According to the ASPCA: Cocoa beans contain the stimulants caffeine and theobromine. Dogs are highly sensitive to these chemicals, called methylxanthines. In dogs, low doses of methylxanthine can cause mild gastrointestinal upset (vomiting, diarrhea, and/or abdominal pain); higher doses can cause rapid heart rate, muscle tremors, seizures, and death. 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 your pet will encounter in any chocolate product. Yet the question of the gravity of the risk presented by this type of gardening mulch remains a matter of debate. According to Hershey's, "It is true that studies have shown that 50% of the dogs that eat Cocoa Mulch can suffer physical harm to a variety of degrees (depending on each individual dog). However, 98% of all dogs won't eat it." Rather than gamble their dogs won't be attracted to the mulch, responsible pet owners will probably prefer to choose another form of soil enhancement for their gardens. The danger of canine theobromine poisoning does not begin and end with cocoa mulch — chocolate in any form poses substantial risks. 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 you keep a pet, do not leave chocolate lying about lest your critter help himself to it and in so doing poison himself. 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. Barbara "canine-one-one" Mikkelson