The oil secreted by the sebaceous glands, which are located beneath the surface of the skin, is designed to maintain skin moisture and softness. In addition, the production of this oil is crucial in maintaining the skin's acid mantle, which is an acidic environment that protects against bacteria. However, an overproduction of sebum can lead to what is known as oily skin. This is characterized by a feeling of greasiness, a "shiny" appearance to the face and, in some cases, clogged pores and acne. According to dermatologist Audrey Kunin on DERMADoctor.com, decreasing the levels of skin oil without depleting the acid mantle or drying out your skin can be a challenge. Theories/Speculation According to dermatologist Audrey Kunin on DERMADoctor.com, the amount of sebum you produce is, to an extent, dictated by your genetics -- specifically, your body's genetically-programmed levels of an androgen called dihydrotestosterone, or DHT. As a woman, your DHT levels are influenced by your menstrual cycle, and correspond with an increase in progesterone after ovulation. DHT first appears in males and females at puberty, and it determines the amount of sebum produced by your sebaceous glands. Prevention/Solution While some of the approaches to preventing or decreasing oily skin are similar to those used for treating acne, not all acne treatments are applicable or appropriate for oily skin. Some interventions may include the use of topical retinoids such as Retin-A or Differin, hydroxy acids such as glycolic acid or salicylic acid, and astringents/toners may be used to prevent or decrease oily skin. According to the Mayo Clinic, excessively oily skin can also be corrected through laser treatments, which act to partially impair the sebaceous glands without harming the skin's protective outer layer. In some cases, a doctor might prescribe a DHT-blocking medication for the off-label use of preventing sebum overproduction. Misconceptions There are some common misconceptions regarding oily skin, how it originates, and how it is eliminated, according to Kunin. One misunderstanding about treating oily skin is that you should avoid makeup while using oil-reducing products. Kunin reports that although you should seek out cosmetics labeled "non-comedogenic" or "oil-free," you don't need to avoid them entirely. Warnings Although excessive oil often leads to the development of acne, it may be unwise to pursue aggressive treatments for severe acne simply to reduce your level of skin oiliness. For example, Kunin does not recommend the use of the prescription drug Accutane for the sole purpose of inhibiting sebum production. The Mayo Clinic notes that in addition to drying the skin, Accutane may cause nosebleeds, sun sensitivity, increased cholesterol, birth defects and suicidal tendencies.