Serums nourish and hydrate the skin without leaving an oily residue behind. They can be used at any time during the day and because of their mostly light properties can be used as great primers underneath makeup. If you are someone who likes to layer on serums after washing your face as part of your skincare routine, there are certain orders in which you should apply your serums. Firstly, never use more that 2 serums per routine. If you are into 4, use two in the morning and 2 in the evening. After cleansing and toning skin, vitamin C serum should be the very first think to touch your skin. If it’s mixed with hyaluronic acid even better.