When you shake your fist in anger on a bad hair day, shake in the direction of your home's pipes. Scientists say copper might be the culprit, per research published in the International Journal of Cosmetic Science picked up by the Telegraph. The dastardly process: Copper found in pipes (or in your hot water tank) leaches into water; wash your hair with it, and over time the metal will build up in the strands' outer layers, where it amplifies the creation of cuticle-destroying molecules. That translates into weaker hair, which makes it more susceptible to things like split ends and fly-aways. If you dye your hair, the effect is worse, they say.
The "they" in this equation is noteworthy, though: They're researchers with Procter and Gamble, which just so happens to be working on creating copper-fighting hair dyes. They looked at hair samples from women living in various parts of the globe, and found that everyone seemed to have it in their hair, at varying levels. "You often can’t see the effects under the microscope, which is why we believe copper has been largely missed as a source of damage," says the head scientist at Pantene. Quirky side note: The Daily Mail reports that a 2012 poll of 2,000 Brits found women endure 26 years of bad hair in their lifetime.