Many situations can lead to the appearance of spots on the skin, such as age spots or those known as melasma. However, they all recognize a common trigger factor, which is chronic exposure to solar radiation. Always protect exposed skin from UV light with a broad-spectrum sunscreen, year-round. This is essential to the success of any product for fading dark spots; plus, it keeps more age spots from showing up.
Everybody's skin is different. Always consult your skincare professional when introducing something new to your routine.