If you have oily skin, it may go against your instincts to use an oil-based beauty product on your face.

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Oily skin may seem bothersome or cosmetically undesirable, but that shiny, slick stuff is actually doing its best to help your hair and skin. As the body's natural moisturizer, oil seals in water, making your hair glisten and your skin smooth. But too much oil can leave your hair appearing lank and dirty, and it may boost acne production in your skin.

Unfortunately, maturity doesn't necessarily free you from oily skin. Your body's sebaceous glands, housed beneath the skin, always produce some measure of a natural, oily substance called sebum. Although some people find that their skin clears up after adolescence -- pimples disappear; that familiar oily sheen gives way to a healthy glow -- other people have to deal with acne and oily skin into middle age. Since oily skin can be linked to hormone levels, women might find that their skin changes during different parts of their menstrual cycle or during pregnancy.

To treat oily skin, many people use cleansers, but too much cleanser, or one that's too harsh, will actually dry out the skin and cause the body to produce more oil in response. In other words, we need these sebum fatty acids to help maintain balance in our skin and hair, so cleanse and wash your face and skin regularly, but make sure to use a balanced, mild product -- twice a day at most. Some cleansers advertise themselves as good for oily skin, but make sure they don't leave your skin red, dry or irritated, all sure signs that you should cleanse less or step down to a lighter product.

That takes care of the cleansing part of our oily skin care routine, but what about all-important moisturizing? If oils are supposed to help the skin and hair retain moisture and you have an excess of skin oil, can you actually use a moisturizer, much less an oil-based one? Quite simply, yes, though most experts recommend first cleansing your skin and then applying a non-oil-based moisturizer. Many moisturizers on the market are water-based, with only a small amount of oil; others claim to be oil-free when in fact they're almost exactly the same as oil-based moisturizers.

So what's the difference? On the next page, we'll look at that question and why moisturizers are important, even for people with oily skin.