"After a bout of breakouts brought on by harsh, cold weather, I tried every skincare product in my arsenal in an effort to get my cystic acne to go down. After two weeks of nothing working, I finally tried the Sunday Riley A+ High Dose Retinoid Serum ($85). Within two days of applying it nightly, the painful bumps on my chin finally started to decrease in size and my overall skin texture became more even and less splotchy. (That's probably thanks to the hefty dose of gentler alternatives to the cell-renewing retinol.) Now that it's in my medicine cabinet, it has earned itself a permanent spot in my nightly skincare routine." — Sarah Siegel, assistant editor, Beauty