Pigmented lesions, or age spots are caused by an increased number of pigment-producing cells (Melanocyte) in the skin. They occur in response to long-term sun (UV radiation) exposure and associated with aging of the skin. The skin tends to get thinner with age. This causes older people to have pale, translucent skin. Melanocytes activity tends to increase and more melanin is produced. Chronic sun damage speeds up the development of these spots.
The melanocytes absorb the energy of the light pulse. This light energy turns into heat energy that coagulates the melanocytes selectively. New cells are later formed without this high concentration of melanin and the skin is renewed.