How would you define dandruff?

Fortunately, we’ve never had to spend that much time pondering dandruff, but if you work for the Advertising Standards Authority in the U.K. you’ve had dandruff on the mind lately, if not the head. The ASA nixed two ads for Procter & Gamble’s Head & Shoulders until they were changed—over what a proper definition of eradicating dandruff is. Text on the screen during the ads says that the shampoo gets rid of “100% visible flakes with regular use” but the problem is that P&G was going with a rather loose interpretation: those dandruff flakes “visible to another person from a distance of two feet” according to a story on the BBC Web site.