Should you try an anti-wrinkle serum?

A lot of people like serums because they feel silky on the skin. They're light, more liquid-based than creams, and they're translucent when they go on. People with oily skin may feel that serums are less likely to encourage acne. We don't really know if that's true yet. Serums are relatively new. They've been in development for a long time, but it's only recently that they've become the hot thing.

How do anti-wrinkle products work? Think of your skin as tiles on a roof. When the tiles dry out, the edges can curve up; that's why dry skin has an uneven appearance. Serums soak into the dry edges of the cells and kind of smooth them out. They reduce the appearance of lines, mainly by moisturizing the epidermis, the skin's outer layer. It's not clear whether they are able to penetrate the inner layers, where the collagen is, to promote new skin growth.

What if I want something stronger? There's a new group of smarter prescription products out right now that contain retinoic acid (commonly known as Retin-A). That's the only thing that has been proved in clinical studies to work for wrinkles, by increasing collagen. Refissa, one of the new products, contains a moisturizer to combat the drying that retinoic acid can cause. Are natural products more gentle? Not necessarily. Botanicals (plantbased ingredients) can be very harsh on the skin. Even essential oils, which are in many natural products, can be irritating if they're not compatible with the pH of your skin. Just because a package says "natural" doesn't mean it's good for you.

What's your best advice for choosing anti-aging skin products? My mantra is that as long as you're protecting your skin with sunscreen and moisturizer, the other stuff is more of a luxury.

—Ellen Marmur, M.D.

Dr. Marmur is a New York City dermatologist and author of "Simple Skin Beauty" (atria, 2009).