As Katt explains to me, oily skin is essentially too much of a good thing, and it manifests when our sebaceous glands begin to produce an excess amount of sebum. (FYI: Genetics, diet, environment, overwashing, hormones, medications, and cosmetics are just a few of the factors that can cause or exacerbate oily skin.)
That said, sebum is important. It helps keep our skin hydrated, healthy, and supple, and it even diminishes visible signs of aging by keeping our complexion dewy and moisturized. In excess, however, it can lead to acne, congestion, and unwanted shine, and using products that are either too rich or overly drying can definitely make oily skin worse.
“Oily skins don’t need additional oil (which is why lightweight or oil-free moisturizers are recommended), but what you do need is water,” explains celebrity esthetician Renée Rouleau. “When the skin doesn’t have the adequate water levels it needs to function properly, it attempts to balance itself by stimulating the nerve endings at the base of the pore. These nerve endings are connected to oil glands and send a message that it’s time to make more oil.” Additionally, Rouleau says that when the oil starts pushing through it may also encounter a clog, triggering bacteria that could potentially lead to a breakout or blemish. Simply put, she says, skin cells are like fish: “They need water to live, and without it, your skin will appear oiler with an increased chance of breakout activity.”