The overwhelming bulk of the info I’ve read said they are toxic. That said if he only nibbled I’d be concerned but not panic.
I suspect (with nothing to make this a certainty), that the confusion (which I did notice) is due to the difference between true geraniums, ones with flowers, and the scented varieties. They aren’t a lot clearer on the differences when you read about them re human consumption but I know rose or lemon geranium for example can both be safely brewed into tea, while you wouldn’t want to eat the other type.
It occurred to me while I was writing this response, the list you might want to post this question to is:
http://www.bio.miami.edu/hare/etherbun.html#otps This question falls into their specialties, and searching the site may give you reliable information, … if not its got a lot of specialists (vets, chemists, biologists) on it so posting should get you some good info.
Best of luck, … please let us know how he does!
PS Sorry I didn’t get back to you, … thank you for the egg yolk explanation, I was very interested!!!