What causes hair to frizz?

Frizz is one of things I get asked about the most—from women with every hair type. And the science behind it’s pretty simple. Frizz is related to the way that hydrogen bonds in your hair are arranged. The amino acids that make up hair contain hydrogen atoms. But moisture in the air contains hydrogen atoms, too. And when these atoms come together and create a bond you get frizz. When you wet your hair completely you disrupt these bonds so they can then be rearranged. And that’s where styling and styling products come in. Styling is your chance to set up hydrogen bonds in a specific way—think of it as “training” for well-behaved hair. You can apply product and then use heat to break your hair’s natural arrangement of hydrogen bonds, which usually involves some amount of frizz. And it’s this rearrangement that is actually creating whatever style you want, whether it’s sleek, straight hair or smooth, bouncy curls.