Strengthening pre-shampoo treatment Olaplex Hair Perfector No. 3 ($28) is one of those products that famous people recommend, even though Olaplex doesn't have celebrity ambassadors. Drew Barrymore swears by it, plus Julianne Hough used it when she permed her hair a few years ago. But it's not just for blondes! Just ask Kim Kardashian West and Yara Shahidi, both of whom have used this reparative elixir.