What It Does:
Coats each strand with detanglers and moisturizers, making hair more resistant to humidity and easier to straighten with products and a blow-dryer. Deposits reflective particles to increase shine. "We also load these formulas with fatty alcohols," says Dianna Kenneally, senior scientist at Physique, "so they detangle as you rinse."
What It Doesn't Do:
Actually straighten hair. "Only heat-styling does that," Kenneally says.
What to Look For:
Shine-enhancing dimethicone for luminous results, and humidity-resistant smoothers like cetyl and stearyl alcohols for frizz prevention.