There is no health benefit to skin bleaching. Results aren't guaranteed and there's evidence that skin lightening can result in serious side effects and complications. From a medical standpoint, there's no need to lighten the skin.

How long does it take for skin lighteners to work?

A lightening agent (for dark spots) like hydroquinone, mulberry, licorice, or kojic acid can begin to work in days, but it usually takes weeks to see an appreciable reduction in pigment. If you see no difference in three or four weeks, it's probably not going to work.

Are skin lighteners permanent?

Changes in skin color will often resolve themselves. For instance, tans fade when the amount of direct exposure to sunlight is reduced. But over time, certain discolorations, such as "age" spots or "liver" spots, become more or less permanent.