A foundation primer may work like a moisturizer only different, or it may absorb oil with salicylic acid or aid in creating a less oily, more matte appearance.[1] It aids in applying the foundation more evenly and smoothly, and increases the longevity of the foundation. Some contain antioxidants such as A, C, and E, or other ingredients such as grape seed extract and green tea extract. There are water-based and silicon-based foundation primers.