Hair Conditioner: Ticket to a Molecular Makeover

Your hair’s sure to feel silkier once your stylist conditions it—learn why with Groupon’s close-up look at conditioner.

Although human hair may look smooth, each strand's outer layer—the cuticle—is actually quite rough. Under dry conditions, the tiny scales that cover its surface become raised and brittle, causing hairs to tangle and lose their shine. Conditioner aims to correct this problem by bonding a particular class of molecules, called cationic surfactants, to the cuticle. This is possible because keratin, the protein that makes up most of the hair shaft, bristles with negative ions, which attract the positively charged surfactants, coating each thread in a thin film that weighs it down and reduces frizz. (The negative charge of keratin is also what causes static whenever positive ions are stripped from the hair—the static that makes it possible to stick a balloon to the wall or to power a miner's headlamp.)

The other ingredients in conditioner don't always need ions to do their jobs well. Humectants suck in water from the surrounding air, thereby moisturizing the hair, and oils simply penetrate the cuticle. Glossers coat the hair with light-reflecting polymers, increasing shine, whereas other ingredients raise the acidity level of the conditioner, which helps protect the hair's protein structure.