Head & Shoulders is a brand of anti-dandruff shampoo produced by Procter & Gamble. Procter & Gamble researchers started making a new anti-dandruff shampoo in 1950. Nearly a decade of research went into making a new formula, which introduced pyrithione zinc into the shampoo. It was first introduced to the U.S. market in November 1961 as a blue-green shampoo formula. There are now nine different Head & Shoulders varieties for varying hair types, and the formula has since changed color to white.
I don't know how they can't know!