The skin produces oil to keep it healthy and moisturized. This oil, called sebum, is produced by the sebaceous glands in the skin. The amount of oil that the skin produces can vary depending on a number of factors, including hormones, genetics, and environmental conditions. Some people may have naturally oily skin, while others may experience increased oiliness due to factors such as hot and humid weather. Overproduction of oil can lead to oily skin and may contribute to the development of acne. To help control oily skin, it is important to cleanse the skin regularly and use products that are designed for oily skin.