Hi,
Acne is often the result of many conditions co-existing, all leading to blocked pores and inflammation. Widely ranging in the severity of the disease, acne occurs on many different skin types.Sebum is a natural production of the sebaceous glands, tiny glands located on almost every part of the human skin.
The production of too much sebum can cause a pore to become blocked, trapping natural skin bacteria and sebum within. Initially, this may appear as a whitehead or a blackhead, two forms of non-inflammatory acne. If the bacteria starts to reproduce, however, the pore quickly becomes irritated and an immune response is triggered, culminating in the redness, swelling, and pain of a pimple.
Avoid over-washing your face because when face is dry the sebaceous glands will actually produce even more sebum to counteract the dryness, and you're back to where you started.
Don't use oil-based makeup or skin products. Widely available OTC bactericidal products containing benzoyl peroxide may be used in mild to moderate acne. The gel or cream containing benzoyl peroxide is rubbed, twice daily, into the pores over the affected region.
REF:http://ezinearticles.com/?Got-Oily-Skin?-Fundamental-Tips-for-Preventing-Acne-Breakouts&id=294600