Our skin colour is a result of melanocytes, cells that store and produce the pigment melanin, which provides pigmentation to our skin, eyes, and hair, absorbs harmful ultraviolet (UV) radiation from the Sun, and even protects other cells from damage due to long-term sun exposure. The amount of melanin produced by the melanocytes differs from person to person, resulting in differences in skin tone. The more melanin you have, the darker your skin tone is. Interestingly, freckles are also caused by clusters of melanocytes in your skin.
The exact cause of melasma is still unknown, but what is known is that it results in an overproduction of melanin. It is suggested that melasma develops after an as-yet-unknown trigger causes the melanocytes to go into “overdrive”. Another theory is that it is due to a “photoageing disorder in genetically predisposed individuals”.
Whatever the actual cause, melasma can be triggered in various ways. The two more common triggers are exposure to sunlight and hormones.