Acne typically develops during puberty, when higher levels of male hormones called androgens increase the size and activity of the sebaceous glands. This in turn raises the skin’s sebum (oil) levels.
Hormonal fluctuations also mean some women experience acne as a component of pre-menstrual syndrome, or during other times of hormonal change, including pregnancy and menopause.
Whiteheads and blackheads occur when pores and dead skin cells become blocked by sebum.
Pimples develop if an inflammation or infection (often with the bacterium Propionibacterium acnes) sets in beneath the blocked pore. Cysts occur if pus and other secretions build up deep beneath the blocked pores within the hair follicles.
The use of certain drugs (e.g. anabolic steroids and some anti-seizure medicines), and exposure to chlorine compounds may also lead to acne problems. Excess iodine may also be involved in some cases.
You’re more likely to be affected by acne if one of your parents had the condition during their teenage years.