All of the factors that affect acne are not completely understood. However the main cause of acne is well known. Excess production of an oily substance that helps keep the hair and skin soft is a prime ingredient. This oil is Sebum, during adolescence the amount of sebum produced by your body is greatly increased. This sebum when combined with naturally occurring dead skin cells can block hair follicles which then turn into an acne lesion. Not only will this mixture block pores it also provides a growing environment for bacteria. It is the growth of bacterial that causes what is commonly called a pimple. The male hormone testosterone is what causes your body to create excess sebum. Testosterone is produced by both males and females. During puberty the increase of testosterone causes the body to have an abnormal reaction which manifests itself with the excessive production of sebum. This excessive oil is commonly found on the facial skin, as well as back and shoulders. In most people the testosterone levels have normalized by the time they are 20 and any acne issues will clear up. Recent studies seem to indicate that acne is at least partially hereditary. In many cases though it is not possible to determine why some people are susceptible to it and others are not. Other contributing factors can be; stress, diet, skin irritation, hormonal changes and some medications. When it comes to diet skim milk seems to be a substantial contributing factor. Many people believe that chocolate, dark soft drinks and greasy foods will cause acne outbreaks. There is not statistical evidence supporting any of those beliefs. Acne can also be induced or aggravated by medications such as; lithium, barbiturates, anabolic steroids and androgens. Recent studies of acne may have found another cause of acne, narrowing hair follicles. These narrower hair follicles can prevent dead skin cells from being expelled from the pore. These trapped skin cells then mix with sebum and bacteria on the skin to form the acne lesions. The are several different issues that can cause the narrowing of the hair follicle, excessive shedding of cells within the follicle, abnormal cell binding and water retention. I is commonly believed that you should squeeze a pimple to remove the blocking sebum as well as the bacteria. This can actually make the problem worse by spreading the bacteria to other areas of your skin as well as possibly causing scarring. This scarring if severe enough can be permanent. In reality touching the area that has acne can actually make it worse as you transfer some of the oil from your hands to an area that already has excessive skin oil. Your hands can also carry bacteria which will aid in the spread of the acne. Your hair can also exacerbate the acne problem by adding oil to areas it touches. It is important to keep your hair clean so it will not contribute to the problems. You should also try to avoid wearing hats and sweatbands as they will help trap the skin oils and just cause more problems.