the cause of acne is not fully understood. though stress can aggravate acne it clearly does not cause it. hormones. common acne in teenagers starts with an increase in hormone production. during puberty both boys and girls produce high levels of androgens the male sex hormones that include testosterone. testosterone signals the body to make more sebum a waxy substance that helps the skin retain moisture. bacteria. excess sebum clogs the openings to hair follicles -- especially those on the face neck chest and back. bacteria grow in these clogged follicles. this makes blackheads or whiteheads form on the skin's surface -- a condition called non-inflammatory acne. sometimes the follicle wall breaks under the pressure of this buildup. when this happens sebum leaks into nearby tissues and forms a pustule -- this is called inflammatory acne. this can create cysts. ruptured cysts can leave temporary or permanent scars. depending on the type of pill oral contraceptives may trigger acne in some women but suppress it in others. steroids taken by some bodybuilders and other athletes can also lead to severe outbreaks. acne has many subtypes. acne neonatorum and acne infantum occasionally affect newborns and infants usually boys. a pimply rash appears on the face but usually clears within weeks with no lasting effect. people who escaped their teen years almost pimple free may develop persistent adult-onset acne as they get older. despite the normal increase in androgen levels during puberty some doctors believe that flare-ups of acne have less to do with androgen levels than with how a person's skin responds to an increase in sebum production. the bacteria propionibacterium acnes and staphylococcus epidermidis occur naturally in healthy hair follicles. if too many of them accumulate in plugged follicles they may secrete enzymes that break down sebum and cause inflammation. some people are simply more sensitive than others to this reaction. sebum levels that might cause a pimple or two in one person may result in widespread outbreaks -- or even acute cystic acne -- in another person.
what causes acne?