It's like any other allergy - some people don't have it, some people have died, and anywhere in between. Repeated, long exposure sensitizes people who are prone, and some woods set just about everybody a-itchin'... a number of luthiers have retired or quit using certain woods, or use masks, goggles & long sleeves, wash their work clothes separate etc. It's definitely real.
Or buy a piece of walnut wood from the hardware store and check in controlled circumstances. Sand the corners off, or make something out of it for fun and see what happens. Just take precautions so nothing horrible happens.
I doubt that drilling a few holes is going to trigger anything, unless you actively SNORT the sawdust... rosewood is actually high on the list of allergy-triggering, danger woods, but I've never seen any warning against guitarists using a rosewood fingerboard. Obviously, it's a problem with particulates, and what turns guitars into particles?!?
Hopefully, not the way you play them.... arty07:
Unless you play with your teeth a la Hendrix and get hyper-stimulated and start EATING your guitar, it's probably OK to merely play a dangerwood guitar. :cool01: Final sanding and finishing might be iffy.