Chocolate and cocoa contain both of the methylxanthines, theobromine and caffeine, which can be toxic to animals if fed to excess. The most dangerous is baking chocolate which contains seven to ten times the amount of theobromine that ordinary milk chocolate does. One ounce of baking chocolate can be life-threatening to a 10 lb dog. The ingestion of approximately 24 oz of milk chocolate would result in a potentially lethal dose for a 27 lb dog. Dogs are more likely to become poisoned by eating chocolate than cats, probably because they like the sweet taste of chocolate and because cats tend to be pickier eaters than dogs.
Health Implications of Eating Chocolate
Even small amounts of chocolate can cause adverse reactions. Reactions can include nervous system stimulation, tachycardia (fast heart rate), weakness, vomiting and diarrhea, restlessness, irregular heartbeat, hyperactivity, and frequent urination. These signs usually appear about 4-5 hours after ingestion. More severe signs of chocolate toxicity include tremors, seizures, and death. Clinical signs may not appear for several hours after ingestion and complete recovery after veterinary care may take several days.
Toxicity studies have shown that compared to other species, dogs are unusually sensitive to theobromine. This is because they have a low rate of theobromine metabolism, which causes theobromine to stay in the blood stream for a longer time. After a single dose, the half-life of theobromine in adult dogs is 17.5 hours, compared to six hours in human subjects. This may also be the case in cats.
If presented with an opportunity, most pets will tend to over-consume chocolate. For this reason, all foods containing chocolate should be safely stored away in areas inaccessible to pets. If your pet accidentally ingests chocolate, consult your veterinarian immediately for advice.