I definitely tell him when I just don't know. No problems with that. It is the how do I know what I know that is harder.
HK- yes he has severe nut allergies. But I really think it has little to nothing to do with that. We have been careful to say that he will just get really sick if he eats a tiny bit..but that we always have the epi-pens with us, and the chances of death are so small if he has an epi-pen that I don't feel like this is lying to him. We can cope with a reaction if needed. Luckily, by having a super OC parent, we have made it five years and only had the one original, first time trying PB reaction. So, I don't think that is something he is too worried about death because of.