Skin discoloration can have many causes, ranging from cosmetic issues to more complex skin issues. The hormones estrogen and progesterone can cause a discoloration known as melasma or chloasma, particularly in women who are pregnant, taking oral contraceptives or on hormone replacement therapy [source: U.S. National Library of Medicine]. Sun exposure can cause tanning and burning, and can make existing skin conditions flare up while damaging your skin.
Some medications have side effects that cause skin discoloration. They might even make you more sensitive to the sun, which can also lead to discoloration [source: U.S. National Library of Medicine]. Also, don't forget about age. Exposure to the sun over time causes age spots (also known as liver spots), which start showing up as you get older. Although these dark places can look like skin cancer, genuine age spots aren't a danger [source: Mayo Clinic].
Skin discoloration can be caused by more complicated underlying conditions. Vitiligo is a condition in which your melanin-making cells stop working or die. The result is patches of white, colorless skin that start out small but then spread [source: Mayo Clinic]. Tinea versicolor is a fungal infection encouraged by warm, humid weather that results in small, discolored areas of skin, which can also be scaly [source: Mayo Clinic]. Increased oil production, fluctuating hormones and a weakened immune system can also help lead to the infection. Morphea results in red or purple spots that discolor your skin, leaving it thick or hard [source: Mayo Clinic]. It tends to strike women more than men, and even though the cause isn't yet certain, the immune system is believed to play a role in the discoloration. Of course, the role sun damage plays in skin cancer is commonly known. Those afflicted might notice some skin discoloration. If you notice any sudden or changing spots, you should consult a doctor [source: American Academy of Dermatology].
Because there are so many different causes of skin discoloration, there are also many kinds of treatments.