Aw man, I had chronic bronchitis all through my 20s and it was *awful*, I empathize with that totally.  I'm so sorry it's so easily set off for you.
I think for me something shifted regarding my immune system because in the same period I also had terrible seasonal allergies - I pretty much couldn't breathe through my nose for a few months out of the year.  Eventually I found a few whack-a-mole fixes for both - if I got a shot of wheatgrass juice right when I felt the bronchitis starting up, and for the allergies, it was bee pollen - I could beat them back with a stick, but they were still always trying to flare up.
But then sometime in my 30s it all just stopped - at the same time that all my food allergies went completely off the charts and my vitiligo started spreading for the first time in my life (vitiligo is that thing where your immune system attacks the melanin in your skin and you end up with patches of no color at all).  I haven't been sick, like, flu, cold, bronchitis sick - in years.  It's like my immune system turned on its head.  And I'm totally grateful for it because I would MUCH rather deal with a restrictive diet and pale spots than chronic bronchitis and 20 sneezes in a row. ;)  Environmental allergens can still set me off, but not at ALL like that "well you're just not going to be able to breathe much this spring, good luck with that" that it used to be; it's a here and there, wildfire smoke or somebody's cologne kind of thing, and not a "the entire season of spring" kind of thing.
All that to say, I don't blame you at ALL for setting your boundaries to keep yourself safe, and your kin are jerks for not respecting that.