To protect himself from the hazards of people taking a possible disliking to him, he's gradually immunized(?) himself to a handful of common venoms/poisons that are used in attacks by the small-doses-every-21-days-or-so technique, such as what snake handlers would do. My question is, does this only work for certain venoms and poisons (ones that are ingested vs. ones that are injected), or can this also be used to protect oneself against the use of knock-out drugs (the ingested and/or injected sort) and that sort of thing?
That asked, I have a few more. How many things can one person immune himself to without it being ridiculous? What symptoms would someone have if they've been injected/have ingested it, but they're immune (sick stomach, a little dizziness, what)?
And how long does the immunity last? Due to being incapacitated for 4 years against his will, he of course doesn't have the opportunity to take those small doses, so would his acquired immunity wear off?
I always feel bad about asking so many questions because it makes me feel dumb and I always end up feeling like "aw, I should've known that," in the end, but right now I'm at a loss. Any help is appreciated. Thanks ahead of time!