Vitamin C is most effective on the skin when applied first thing in the morning. It strengthens our defenses against UV rays and free radicals, which are the main causes of photoaging and which we are exposed to most of the time during the day. Vitamin C can help repair and speed up healing in the evening, but since ascorbic acid has a reservoir impact (lasting up to 72 hours), it is usually unnecessary. It's all about successfully arranging your resources. However, some antioxidants, such as Resveratrol, have been demonstrated to be more effective at night.