Melasma, more commonly known as "the mask of pregnancy," is brown pigmentation on the cheeks, around the eyes and sometimes on the forehead or above the lip. It is most often caused by the hormonal changes or fluctuations of pregnancy, which make your skin more likely to develop dark patches of pigment when exposed to sunlight.
However, melasma can occur independently of pregnancy and can even affect men. Asian skin is particularly susceptible. Other activities or conditions that contribute to the condition include waxing of facial hair (especially above the lip), allergic reactions to skincare products or other inflammations. Above all, sun exposure can worsen the dark pigmentation.
The best way to avoid or minimize melasma is to wear sunscreen-- all day, every day, year-round. You may not feel that you spend a lot of time outside, but even incidental exposure (such as through your car window) can exacerbate melasma. Choose an ultra-broad-spectrum sunscreen that blocks both UVA and UVB rays. UVA rays in particular contribute to darkening of the skin and can even permeate windows.
There are many outstanding sunscreens on the market today. One of the best is Coppertone Sport #48 in the blue bottle. It withstands vigorous physical activity and dries like a powder. For everyday use, a good one is Solbar AVO with Parsol 1789. For those who wear makeup and need to avoid waterproof sunscreens, some good choices are Avon's Day Force or Age Block with Parsol 1789. Estee Lauder's chemical-free sunblocks are great for those with sensitive skin who prefer physical blockers like zinc or titanium dioxide. If you're pregnant, however, you should consult your OB/GYN before using any products, even topicals like sunscreen.
Once you're using sunscreen religiously, your dermatologist can identify a regimen to help clear up your melasma as soon as possible. She may begin with either Retin-A or Neostrata's glycolic acid lotion, depending on skin sensitivity. These exfoliators can be coupled with hydroquinone, a bleaching agent (either a prescription product or Neostrata's bleaching cream, which contains both glycolic acid and hydroquinone).
For more stubborn cases, dermatologists also prescribe a high- or mid-potency steroid cream. This should only be used in conjunction with Retin-A or a glycolic acid product, though. Steroid creams can thin the skin or cause broken blood vessels if overused, but both Retin-A and glycolic acid have been shown to eliminate these negative effects. A series of physician-administered glycolic acid peels (anywhere from three to ten, depending on the severity of the condition) can also help clear up melasma. Generally lasers are not an effective treatment for melasma -- they often exacerbate the condition by making the affected area darker.
Once you and your dermatologist have determined the best regimen for you, your melasma should be gone within three to four months. You must continue to wear sunscreen every day, though, if you want to maintain the results.