Not long ago, I was standing in my bathroom, scanning the ingredients list on my go-to hand cream. Retinol? Nope. Vitamin C? Not here. But tucked somewhere in the middle of the list was glycerin. Then ...

When your skin feels itchy and tight, you likely reach for a moisturizer made for dry skin. Or maybe you pick up a serum infused with hyaluronic acid, a humectant ingredient known to hold a thousand ...