Creams containing hydroquinone are used to spot lighten skin due to sun exposure and aging, although some individuals use the creams all over their bodies to lighten overall skin tone. Over-the-counter lightening creams regularly contain 2 percent hydroquinone. Prescription creams contain 4 to 6 percent.
Combination creams available by prescription may contain tretoinin, in addition to hydroquinone, to treat melasma, a condition where the skin darkens due to pregnancy. Melasma may also occur during oral contraceptive use, or if women are undergoing hormone replacement therapy after menopause.
One ingredient to avoid is mercury. It is banned in skin lightening creams sold in the United States, but it may appear in creams sold outside of the country. While mercury is a known melanin-inhibitor, it is also a toxic agent that can cause neurological and psychiatric problems, in addition to many kidney problems.
Lightening creams work by reducing the amount of melanin in the skin. Melanin is a pigment that gives skin its tone. The darker the skin, the more melanin it contains. The amount of melanin in skin is controlled by one's genetic makeup, though sunlight exposure, hormonal fluctuations, skin damage and exposure to certain chemicals can also affect melanin production.