Thanks-- but let me reiterate that our strategy is probably not the correct one under all circumstances, and we see a
very fine board-certified allergist, with whom we work closely.
Still, all of this stuff is a work in progress all the time. That allergy bucket/cup thing is all too real, unfortunately. So is the allergic march. A lot of clinical practice in this area (not the pharmacology, of course, but the bigger-picture stuff touched upon) is hypothetical at best, unfortunately.
There's
no way that H1/H2 receptor therapies are anything like a magic bullet for preventing serious systemic responses to life-threatening allergens. HAVE to say that. I know that everyone who has participated in this thread thus far is well aware of that, but over the years, I've heard some pretty wacky ideas, and that's definitely one of them that I hear a lot.
My daughter and I both take high doses of cetirizine daily, and we've both anaphylaxed pretty floridly while doing so in spite of that "protection." It can definitely happen, and exposure to an allergen that you have life-threatening history with is just not a good idea without specific, expert medical guidance.

This stuff isn't even a DIY project for someone like me; I treasure our partnership with our allergist, and we are VERY compliant patients.