Known for tackling everything from acne to wrinkles, retinol has earned its reputation as a powerhouse anti-aging skin care ingredient. But there’s a lingering rumor that this form of vitamin A can thin the skin , causing some to hesitate to incorporate it into their regimen. We spoke with dermatologists to explain what’s really happening, and whether you need to worry. The idea that retinol thins your skin likely comes from some of the short-term side effects it causes when you first start