|Source: Kenny Louie (CC BY SA: 2.0)|
Coffea robusta, which is native to West Africa, contains a greater amount of caffeine and other active constituents because of how it is processed. In a study of 35 women aged 30-70, they were instructed to apply a caffeine-containing eye cream to the area around one eye twice a day, and not to the other half. After four weeks, there was a significant improvement in smoothness and wrinkle depth in the treated halves of their faces. This was measured with a 3D optical imaging technique. In research on mice, caffeine was also found to prevent damage caused by UV light.
If you are having trouble with dry, rough skin that doesn't seem to be protecting itself enough, coffee may be best paired with honey. Honey is a humectant, which means it helps trap moisture, much like the glycosaminoglycans that coffee supports the production of. As it is sticky, it also makes a great addition to any home-made face masks because it would help keep the other ingredients stuck to your face.