Sunspots, which are also known as age spots can be treated topically with hydroquinone up to 4%.
The hydroquinone will block an enzyme that is needed to make melanin (the pigment you see in sun spots).
The disruption in the process causes the structures in the skin which contain the melanin to break down.
And this results in a fading of the age spots.
However the FDA has imposed a limit of 3 months regarding the continuous use of hydroquinone. Past this point, it can be toxic.
Laser treatments offer a safer, faster and more effective alternative. If there are a small number of age spots they can be treated with Q-Switched Nd Yag lasers. Larger areas will require a system like Fraxel Dual.
Laser energy will break up the pigment and the specialized cells containing them. And your body removes the remains through the blood and lymphatic system.