• exposure
  • Targeted sun exposure, for example someone who might drive long distances for work, may also contribute more apparent hyperpigmentation on one side of the face, neck and arm (again, don't forget that UV rays can reach us through glass). (obagi.com)
  • especially
  • Chemotherapy-induced hyperpigmentation is caused by many chemotherapeutic agents (especially the antibiotics bleomycin, and daunorubicin) and the alkylating agents (cyclophosphamide and busulfan). (wikipedia.org)
  • conditions
  • Hyperpigmentation is associated with a number of diseases or conditions, including the following: Addison's disease and other sources of adrenal insufficiency, in which hormones that stimulate melanin synthesis, such as melanocyte-stimulating hormone (MSH), are frequently elevated. (wikipedia.org)