Between poolside chemicals and over-styling to combat the humidity, summer can wreak havoc on your locks. We're always in awe of Taylor Swift’s glossy strands so we asked the singer what she uses on her hair to keep it looking soft and healthy. She told InStyle.com "I don't use any hair products, except for shampoo.” Her must-have? Kerastase Bain Apres-Soleil Shampoo ($36; kerastase-usa.com,) a light cleanser that quickly detangles and softens hair. “This is my favorite," she adds. For more celebrity hair must haves, check out our gallery!