AHA and BHA products, in concentrations for AHAs between 4% to 10% and BHA in concentrations of 1% to 2%, can be effective by not only accelerating cell turnover of the top layers of skin but also by directly inhibiting melanin formation. That makes them a formidable asset in reducing or eliminating the appearance of brown discolorations. (Source: Experimental Dermatology, January 2003, pages S43-S50.)
As part of a skin-care routine, in combination with other treatments such as kojic acid, hydroquinone, azelaic acid, and laser resurfacing, AHAs or BHA can be very effective for improving the overall appearance of sun-damaged skin, inhibiting melanin production, increasing cell turnover, and helping other skin-lightening ingredients penetrate the skin better.
Physicians and aestheticians can apply AHA, BHA, or trichloroacetic acid peels in varying concentrations to improve the appearance of skin discolorations as well. (Sources: Journal of Dermatology, January 2007, pages 25-30; and Dermatologic Clinics, July 2005, pages 353-362.)
Although AHA and BHA peels are popular procedures, cryotherapy is an inexpensive procedure in which the brown skin discoloration is burned from the skin, usually with liquid nitrogen. This has been shown to have better efficacy than peels, but although cryotherapy was more likely to produce substantial lightening it was more painful and took more time to heal. (Source: Journal of the European Academy of Dermatology and Venereology, March 2008, pages 316-319.)