Chocolate can be deadly to cats because it contains theobromine and caffeine, both of which are toxic to them. Cats cannot metabolize these substances effectively, causing them to accumulate to dangerous levels in their bloodstream. Even a small amount of chocolate can cause serious health problems, including increased heart rate, vomiting, diarrhea, seizures, and potentially death. Dark chocolate and baker's chocolate are the most toxic due to higher concentrations of theobromine, but all types of chocolate, including milk and white chocolate, should be avoided. If a cat consumes chocolate, immediate veterinary attention is necessary. Cats usually do not seek out chocolate because they cannot taste sweetness, but chocolate should always be kept out of their reach to prevent accidental ingestion.