[cguess]

"feelings of dizziness and being lightheaded" sounds much more like a tourist was walking around Italy in the summer with a heavy backpack and not drinking enough water after getting off an airplane and probably impinging too much wine at dinner the night before.

[jjkaczor]

Same with any hotter climate tourist location and 'mysterious syndrome'.

Also combine with perhaps a little change in their stomach biome from drinking different water and/or eating different dairy products, making them more easily dehydrated.

[cguess]

People tend to either over or under indulge while traveling too (I always lose weight when I'm on the road myself) and that's never awesome in either direction