DreadPirateMurphy
Explorer
I'm not really worried about anyone eating or drinking something that their "host" might be allergic too.
I mean, come on, think about it . . . whoever the brass pick to be your "host", if they have any serious allergies that you could inadvertently trigger, they'd tell you about it.
"Welcome home to Earth Eli. While you're here in Sgt. Central Casting's body, be aware he has a severe allergy to peanuts. Go have fun!"
You're assuming that they've thought through all of the ramifications of having untrained civilians using ancient technology in an unexpected and high-stress situation. The original plan was probably not to use the stones for R&R purposes by non-military personnel.