Topical lightening composition and methods of use thereof

A topical composition for reducing pigmentation in human skin, comprising:

• (i) 3,3′-thiodipropionic acid, or a salt or ester thereof, and (ii) nicotinamide, or salt thereof, or melanosome-transfer inhibiting derivative thereof, and (iii) a cosmetically or dermatologically acceptable vehicle,
• wherein the 3,3′-thiodipropionic acid, or salt or ester thereof, is present in an effective amount ranging from about 0.1% (w/w) to about 2.5% (w/w) based on the total weight of the composition and the nicotinamide, or salt thereof, or melanosome-transfer inhibiting derivative thereof, is present in an effective amount ranging from about 0.01% (w/w) to about 1% (w/w) based on the total weight of the composition, and
• wherein the effective amount of 3,3′-thiodipropionic acid, or salt or ester thereof, and effective amount of nicotinamide, or salt thereof, or melanosome-transfer inhibiting derivative thereof together provide at least 25% greater relative reduction in melanin synthesis than either component alone.