When does the color of the nipple typically darken, and what causes this change?

The darkening of the nipple's color is primarily influenced by hormonal changes, particularly during puberty and pregnancy. During puberty, the increase in hormones such as estrogen leads to a higher production of melanin in the skin, which can cause the nipple and areola to darken. This response is a natural part of breast development as the body prepares for potential future breastfeeding.

Although other factors can temporarily influence skin color, such as sun exposure, they do not explain the physiological changes associated with nipple darkening as effectively as hormonal influences during significant life stages like puberty. During lactation, while hormonal changes continue to play a role, the initial darkening is more closely associated with puberty. Therefore, the hormonal changes related to increased melanin production at puberty provide the most accurate and comprehensive understanding of why this phenomenon occurs.