Hormones and genetics
At the start of puberty, androgen hormones are released into the body. Both boys and girls have androgens, but boys have more of them. Androgens cause the oil glands in the skin of the face, neck, back, shoulders and chest to enlarge and to produce more oil (sebum).
Bacteria that normally live on the skin surface digest the oil and by-products from this digestion irritate the skin, block the pores and produce blackheads, pimples and cysts.
Girls tend to reach puberty earlier than boys and develop acne at a younger age. Acne can become worse or ‘break out’ at certain times of a girl’s menstrual cycle, usually just before a period.