Believe it or not, moisturizer is beneficial for oily skin. Sebum provides lubrication to the skin, not moisture. Moisturizers are important because they provide ingredients that can be absorbed into the skin. Sebum, on the other hand, comes out of the pores to lubricate the skin, sealing in the moisture. After you cleanse and tone with products designed to combat oil, your skin may be a little dry. When moisturizer is not used, sebum goes into overproduction; it is making an effort to quickly prevent the loss of the remaining moisture in your skin. This is in addition to the usual overproduction of oil you commonly experience. Moisturizers can reduce the overproduction of oil and minimize an oily appearance. Moisturizers that are oil-free and contain salicylic acid help prevent oil buildup and moisturizers that create a matte absorb and combat oiliness.