The skin condition is notoriously difficult to treat. It is sometimes called the "mask of pregnancy," which is actually a misnomer since childless women and men can also get it. Latinos, Asians, and the Irish are particularly susceptible.
Like many sufferers, Maria has tried just about everything to clear it up.
"I've tried using some bleaching cream, some lemons, some limes--nothing worked," she tells CBS 2's Paul Moniz.
Last fall, Maria learned about a clinical study at Mt. Sinai School of Medicine that was testing the effectiveness of microdermabrasion, commonly known as a skin sanding.
For the past 11 months, Maria has received seven 15-minute treatments during which aluminum crystals are sprayed at her skin under high pressure and then suctioned off, removing dead skin.
The treatments fade the brown patches.
"It increases blood flow to the skin, causes some swelling in the skin, and some inflammation," explains Dr. James Spence, who treats Maria. "That biologic response clears this pigment away."
The dermatologist, once a microdermabrasion skeptic, says the painless procedure may offer only mild benefits for fine lines, but dramatic improvement for melasma.
The big downside to microdermabrasion is cost. Each treatment can run $100 to $200. It may take five or six treatments to get the melasma under control. The treatment is not permanent. Maintenance touch-ups might be needed two or three times a year. Insurance does not cover the treatment.
Because microdermabrasion is considered a cosmetic procedure, it is not regulated by the FDA. Some salons offer it, but patients are safest seeing a dermatologist to prevent bruising.
In an ongoing study of 30-plus patients, Dr. Spencer says he has seen significant improvement in 75% of the cases. He combines the treatment with bleaching creams and strong sunscreens.
But even that trio is little match for the sun. All it takes is a few short exposures and the melasma slowly returns.
Before her treatments, Maria had a large dark patch running the length of her cheek. After six treatments, with no wounds or downtime, her skin was nearly clear. And additional treatments faded the dark patches that Maria developed on her cheeks from too much sun on a recent trip to Puerto Rico.
"Now, everyone looks at me and says, "Wow!" My face glows. They say, "What did you do?" she enthuses.
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