What does "immediate pigment darkening" refer to?

"Immediate pigment darkening" refers specifically to the darkening of preexisting melanin in the skin that occurs directly after exposure to ultraviolet (UV) light. This process is part of the skin's natural defense mechanism against UV radiation, where existing melanin absorbs the light and darkens, resulting in a tanned appearance almost immediately.

This response is distinct because it does not involve any external products, such as tanning lotions, nor does it pertain to the delayed response of tanning that typically takes longer to develop, like changes due to initial sunburn or dark areas appearing after a certain period. Instead, it highlights the body's immediate reaction to UV exposure and the activation of the melanin that is already present in the skin. Understanding this mechanism is crucial for comprehending how tanning occurs and how melanin functions as a natural protector against UV damage.