Just because it's pricey and comes in a pretty jar, it doesn't necessarily mean a product has more effective skin care ingredients.

Often, "lower-priced products may work better than their more expensive counterparts," says Arthur W. Perry, MD, author of the book Straight Talk About Cosmetic Surgery. Whether it's $9 or $99, here are three key ingredients to consider...

3 Proven Ingredients
According to Dr. Perry, vitamin C (also known as L-ascorbic acid), alpha-hydroxy acids (also known as AHAs, fruit acids, and glycolic acid), and retinoids or retinol-like compounds (tretinoin, retinol, etc.) are a few of the handful of skin product ingredients backed by strong scientific evidence that they boost skin health and appearance.

What About the Rest? That doesn't mean other ingredients won't benefit your skin; it's just that the scientific proof isn't as solid for them. The main reason some skin care ingredients fail to deliver? Their molecules are too big to penetrate your skin when applied topically.

(Find out which skin care items are best for your skin.)

Other useful ingredients: polyhydroxy acids, beta hydroxyl acids, hydroquinones, and certain antioxidants. For more on skin care ingredients that have scientific heft, check out Dr. Perry's book.