I was using a tube of concealer a week. The reason? The blotchy, dry skin I was trying to camouflage.

I saw a dermatologist, who in her understated way said, “Your face looks a little dull.” She sent me home with a bottle of Prevage MD. The active ingredient, idebenone, is said to be an antioxidant that protects and repairs skin cells. I was to use it every night for a month.

Many “magic” potions don’t seem to do a thing. Still, squirting out that first blob of what felt like marshmallow fluff, I was optimistic. It went on silkily as I rubbed it in with a fingertip—on my forehead, nose, cheeks, chin, pretty much everywhere except around my eyes.

There were some subtle but immediate effects. My skin seemed brighter and softer. A week later the blotchy red patches were gone. Fine lines and brown spots, from all those years of going outside without sunscreen, were slightly less noticeable, and my skin tone was more even. My fortysomething face didn’t look dry and dull but clear and polished.

The Prevage MD I bought at my doctor’s office is not quite the same as the Prevage sold in stores or through Web sites like Amazon.com. Prevage MD contains 1 percent idebenone, while the over-the-counter version has half that. A one-ounce bottle of Prevage MD averages $100 to $120 through local dermatologists; a 1.7-ounce bottle of 0.5-percent-idebenone Prevage costs $150 in stores.