Jennifer Yen, an actress and beauty expert who founded purlisse, tells me that in addition to the aging factor and lack of hygiene, "skipping out on proper skincare can also make an already uneven skin tone worse. This is because your skin regenerates at night as you sleep, so depriving it of ingredients known to combat pigmentation means that any recourse for skin damage has been removed. The same principle applies to age spots/dry spots too."