>Sometime mid-summer I stopped by a barber and before I'd realized it he'd squirted a glob of shampoo onto my head. It was too late to protest, so I just sat through the scrubbing. For the following 2 weeks my hair was a mess: full of dandruff and totally uncontrollable. I find this hard to believe. My money's on confirmation bias.
My blond, 3-4 inch long hair is shiny and lays on my head just fine. When I wash it.. its about two days before it goes back to being the same. Mostly it gets frizzy, but my scalp will also dry out to some degree, so I wouldn't be surprised if someone had increase dandruff.. though there is probably a bit of hyperbole going on here.