Using niacinamide and vitamin C together? The old myth comes from a 1960s lab experiment - it has nothing to do with your actual routine.

Mild tightness is normal, burning isn't. Here's how to introduce retinal safely on sensitive skin - and know when to pause.

If you have sensitive skin, "just try retinal and see how it goes" is not good advice - and you already know it. What you actually need is a way to tell a normal adjustment...