Chocolate contains two toxic compounds called caffeine and theobromine. Humans have a higher tolerance and rarely suffer form chocolate poisoning. The theobromine concentrations vary in different types of chocolates - it's easiest to remember that the darker the chocolate, the more dangerous it is.
Symptoms of chocolate poisoning in your dog are;
- Increased heart rate
- Increased/inappropriate urination
- Seeming agitated
- Erratic Breathing
- Seizures/Collapse (if left untreated)
For cats - chocolate is usually more toxic, but since they can detect the sweetness, they are very unlikely to consume it.