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.
Once they can read, though-- they DO pick it up casually and from the media.
YOU may never have said "this could kill you, you know..." but it's possible that he has determined this from sources other than you. It may also not be the best idea long-term to DENY the potentially fatal aspect-- just noting that this can lead to trust issues later when they discover that your early explanations were lies of omission. Just something to consider there.
I know several people who have had this happen with their school-aged kids in the wake of a major news story about a fatality. With HG+ kids, it's a real concern because they are simply nowhere near as oblivious to adult conversations as those adults often seem to think that they are. Teachers, sitters, family friends, etc-- basically anyone that knows that your child has an epipen can do it out of the blue. There isn't any "unhearing" those things for our kids, either. KWIM?
It's amazing the kinds of insensitive things that get said around kids, sometimes. I mean, they aren't oblivious! I've also found that my DD sometimes doesn't tell me for a few weeks about things that bother her. (Thinking about the art class instructor that informed her that she should "see this chiropracter" she knew, for a "cure" for her allegies, for example... this REALLY bothered her because she thought that maybe it was real-- she was four-- and that perhaps we didn't care enough to cure her, or that we didn't KNOW about this cure, and that called into question our competence, her specialists competence, etc. Aughhh.)
If this is (or is ever) an issue that requires addressing, one helpful tip is to offer 'differentiating' characteristics to your child in a way that reassures him/her that s/he is NOT going to become a statistic. "We always carry your epinephrine, even if we don't think that we will be eating anything." "It sounds like this person needed a LOT less of the allergen than you have in the past in order to cause a reaction like that." "This is why we are always careful to ask questions in restaurants." "It sounds as though this person didn't get help from her friends right away when she knew she was in trouble, huh?" I also play the doctor-expert card periodically with particularly nasty issues, like the one with the artsy teacher that thought that woo was the solution...
The bottom line is that focusing on how
preventable most of those fatalities are can be helpful to kids with life-threatening medical conditions, but only up to a point. Beyond that point, they have to develop the emotional resilience to manage those realistic concerns that are extraordinary, and to do so with healthy coping. It can be a tall order.