Acne is often caused by high androgen levels (male sex hormones). Having a slight hormonal imbalance can cause your sebaceous gland to produce an excess of sebum oil which is a primary cause of acne breakouts.
Birth control pills can help by regulating hormone levels which in turn will lead to a reduction in the levels of sebum oil. Sebum is an oil that is lubricates your hair and skin. Acne breakouts occur when a build up of sebum and dead skin cells block the skin pores and allow bacteria to flourish. As birth control pills only target one cause of acne, the excess sebum oil, it is often best to use them in conjunction with other acne treatments which contain benzoyl peroxide or salicylic acid (such as the Exposed Skin Care Facial Cleanser and Acne Treatment Serum). It may be necessary to take the pills for quite a few months before any results are noticeable and your skin may get worse before it gets better.
Using birth control pills for acne treatment does carry a risk of side effects. They can cause headaches, breast tenderness, changes to the menstrual cycle and also increase the risk of blood clots, high blood pressure and heart disease. It is unwise to take birth control pills if you have a history of any heart problems or cancer. Of course it is also necessary to see your doctor before beginning a course of the pill.