Which factor has a longer lasting effect on pigment darkening?

The factor that has a longer lasting effect on pigment darkening is PPD, or Persistent Pigment Darkening. PPD refers to the biological process that leads to the darkening of the skin pigmentation as a result of exposure to ultraviolet (UV) radiation. Unlike UVA and UVB rays, which primarily cause immediate tanning effects through different mechanisms, PPD leads to a more prolonged effect.

UVA rays penetrate deeply into the skin and are known for causing immediate tanning, but their effects tend to fade relatively quickly. Similarly, UVB rays are responsible for the initial redness and sunburn, but their tanning effects are also not as long-lasting as those caused by PPD. Infrared radiation is more associated with the heating of the skin and doesn’t directly contribute to the tanning process or pigment darkening in the way that PPD does.

Understanding this difference is critical for tanning professionals, as it informs them about how to better guide clients in their tanning practices and provides insight on how long-lasting results can be achieved safely.