Fred's been very good with the Christmas tree this year, hasn't he, dear? Yes, he hasn't touched any of the chocolates... Or presents! He's such a good boy! Yes, he is, isn't he? I'm just biding my time!
Chocolate contains theobromine, which is similar to drugs given to asthmatics. It can cause seizures and heart arrhythmias, among other things. The darker the chocolate, the more toxic it is. Chocolate can be toxic to humans, too, but you’d have to ingest an enormous amount of it to cause a problem. It’s also toxic to cats, but cats are much less likely to ingest it. .