Did you know that uneven skin tone can add up to 12 years to your perceived age? It's also, according to this story in The New York Times, catching up with dry skin and wrinkles as one of women's biggest skincare concerns—more than one-third of American women are worried about it. In some ways, I think this is a great development, because it shows we're thinking more about the quality, texture and luminosity of our skin, instead of single-mindedly focusing on wrinkles (and covering up everything else with heavy makeup). But I hate to break it to you: Uneven tone is also one of the trickiest beauty problems to solve.
Blotchy pigmentation can come about after hormonal changes like pregnancy or a stint on the birth control pill. Sun damage is also to blame, and then there are those of us who get the pesky dark marks (called post-inflammatory pigmentation) that come after a blemish and can linger for MONTHS.
Unfortunately, no product is going to even out your complexion overnight. Nor is there one single ingredient that you should look for. (Hydroquinone, a bleaching agent, used to be the gold standard, but it's falling out of favour because some studies link it to increased cancer risk. So not worth it.)
Instead, you should look for brightening products that contain a variety of ingredients, all of which inhibit melanin production: Soy, mulberry, vitamin C and kojic acid are a few of the players. I've used Dermalogica Night Bright (now discontinued and replaced by Pure Night), Ole Henriksen Truth Serum and Medique Vitamin C Serum with good, although not miraculous, results. (Tip: If you suffer from post-acne marks, start applying the serum the minute the blemish has resolved.)
Of course, you should always see a dermatologist if you have more pronounced hyperpigmentation or age spots. He or she may give you a prescription-strength retinoid or hydroquinone product... but the former can be tough on sensitive skin and cause redness (and the latter, as I said, I'm not a fan of).
Intense pulsed light treatments can also help resolve uneven skin tone, but know that you're looking at a series of treatments, which can get costly. Chemical peels are another option, but I'm on the fence about all this hyper-exfoliation. The idea is that removing the upper layer of dead skin cells will reveal brighter, more even skin underneath. But in my experience, you can risk even more pigmentation problems if your skin happens to flake off too quickly post-peel. That's what happened to me (just from normal face-washing, a couple of days after my low-grade peel), and I developed a dark patch on my skin that made my complexion look worse than it did before. Then there's the other issue—that if you have too many peels, they'll also weaken your skin and leave it more fragile in the long run. You'll also be more vulnerable to that very sun damage you were trying to avoid. No thanks!
I think, as with most things in life, it's best to stick to the basics. Exfoliate gently a couple of times a week and use a brightening serum or moisturizer. Use sunscreen, but don't rely on it to protect you all day—it's even better to just stay in the shade. Address the underlying cause of hyperpigmentation problems (if it's something like persistent hormonal acne, for example). It can take up to four months to see results, so most of all—although I know it's not the answer you're looking for—be patient.