Acne can be very upsetting physically and emotionally,
It can happen at any age.
It can happen to any gender.
Likely causes of Acne are:
Hormones: too much Testosterone, DHEA.S, Estrogen. Teenage, pregnancies or oral contraceptive pills are likely usual causes.
PCOD: Polycystic ovarian disease is of above hormones out of whack in addition to excess hair growth also contributes to acne and this cause is generally treatable.
Teenage: again basically hormonal surge during teens, usually self-limiting.
Stress: Not a known documented cause but this is a hypothesis: The way stress can increase acne is increasing stress hormones that leads to excess oily skin and sebum production leading to acne, can be treated by reducing stress and meditation.
Genetics: If your parents had it you are likely to inherit that gene of acne.
Food: Surprisingly study shows chocolates are a cause of acne, otherwise foods generally not the number one cause,
Smoking: Conflicting studies show conflicting point of views; in fact one study in 2007 showed that smoking in adolescents may be anti-inflammatory and decrease acne, well whatever studies say, smoking is a bad idea from every point of view. I will stick with the harmful effect on acne.
Usual medications to treat acne range from benzoyl peroxide, retinols, topical clindamycin/erythromycin, and systemic antibiotics of tetracycline class like doxycycline or minocycline.
What really might work for very cystic acne are acid peels or lasers done by professionals and dermatologists, derma abrasions are reserved for scarring.
Newer dermatologists everywhere are brining in new technologies for a clearer skin, so an appointment with a dermatologist is totally worthwhile, if someone you know has been to a dermatologist already its better to take feedback before you visit them.