1.   Her skin had darkened over the years.

2.   His skin permanently darkened and eyes essentially blinded, he received minimal health care.

3.   Place on grill or under broiler until softened and skins have darkened and blistered.

4.   Arbutin, the active compound in bearberry, is also able to cure hyperpigmentation or skin darkening, which is due to the inhibition of melanin biosynthesis.