Image source: http://img.medscapestatic.com/pi/features/slideshow-slide/identifying-lesions/fig6.jpg?resize=645:439
This condition is not dangerous or serious, but it is completely irreversible. Once the spots form, there is no way medical or esthetic to reverse the damage. The best way to treat is to prevent further damage by properly using sunscreen.
That being said, there are three ways to mask the damage.
1. The first is the application of self tanners. Self tanners will, temporarily, dye the skin cells and cover the hypopigmentation. You can have these products applied professionally, or you can do it yourself at home (but be careful, watch for streaking!)
2. The second is the application of permanent makeup to cover the damaged areas with pigment. The permanent makeup artist will match the color to your skin tone, and usually the damaged area is completely neutralized by the application.
3. By using microdermabrasion and chemical peels to neutralize the hyperpigmentation (dark spots) you can see an improvement in skin tone, as the lighter patches do not stand out as noticeably.
Lastly, these solutions apply to hypopigmentation spots caused by sun damage; there are several other causes for hypopigmentation, so it is best to consult a medical professional to rule out the following conditions:
Vitiligo: Vitiligo causes smooth, white patches on the skin. In some people, these patches can appear all over the body. It is an autoimmune disorder in which the pigment-producing cells are damaged. Symptoms of vitiligo include an often rapid pigment loss in several areas of the skin, and it is more common in dark skinned individuals.
Tinea Versicolor: Tinea versicolor is caused by a fungus. This fungus lives all around us, including on the skin. Symptoms of tinea versicolor include small, flat, round or oval spots that may, over time, form patches. The spots occur on oily areas of skin on the upper chest, back, or upper arms or, less often, on the upper thighs, neck, or face. The spots can be lighter or darker than the skin around them. This condition can be very tricky to diagnose, so make sure you consult a medical professional if you suspect you have Tinea Versicolor.