Nicknamed "liquid gold" in Morocco for its many beauty benefits, this oil—which comes from the kernels of the argan tree—is loaded with vitamin E, essential fatty acids, and proteins. It's amazing in products because it's ultra-hydrating for skin and strengthens hair, but it's also a great nail treatment on its own. "If your nails are brittle or peeling, soak them in a small bowl of pure argan oil, available at health-food stores, for 10 minutes every day for a week," suggests dermatologist ...