With ageing, the number of melanocytes in the skin reduces. The melanocytes that are left undergo a compensatory increase in size, and they then focus on specific areas. This process is responsible for the development of age spots in people over the age of 40.
Injuries to the skin
After injuries to the skin which include surgical incisions, burns, and chemical injuries, the skin undergoes a darkening due to the stimulation of melanocytes in response to injury. The skin develops post-inflammatory hyperpigmentation as a result.
Certain medications can cause hyperpigmentation, including antibiotics, antidepressants, chemotherapy drugs, and anti-epileptic drugs. Medical conditions that cause hyperpigmentation include Addison’s disease and Diabetes. Vitamin deficiencies can be a cause of hyperpigmentation.