Are they Scarlet Runner Beans?
I only know them as 'runner beans', but looking at the images on Google, which shows red flowers, then I think they probably are. We got away without any side effects this time, and as far as I can tell, it's the beans themselves which are the issue, and the more mature/red/hard they are the worse it can be. Luckily at the moment, the beans are little more than small white seeds, and it's the pods that are so delicious he's been eating them raw straight from the fridge. One for the future, though, and as I've always whined that my husband leaves them on the plant so long that the pods are tough, it does mean that from here on in they'll be picked nice and young - and only eaten raw occasionally, with the beans removed!