Common causes of oily skin include overuse of skincare products, hormonal changes and some medications. Additionally, some people are genetically predisposed to having oilier skin than others.
Many people use a variety of skincare products, such as acne cleansers and exfoliating washes, in an effort to make their skin look younger or smoother. Using too many of these products or scrubbing too hard while using them may damage the skin and cause it to secrete excess oil. Some people also use the wrong products for their skin type. Using a product for oily skin on combination skin, for example, may strip the skin of its natural oils and cause it to produce excess oil in an effort to compensate for this loss.
People whose parents suffer from oily skin are more likely to have oily skin themselves. Often, this is simply a case of having larger sebaceous glands; the larger the glands, the more oil they produce. In women, the sebaceous glands are also more active during menopause, when excess androgens cue them to produce more oil. Some women find that their skin is more oily at the onset of their menstrual cycle or while they are pregnant. Stress may cause hormonal imbalances that make the skin appear oilier than normal. Medications such as birth control pills, which alter hormone levels, may increase oil production, too.