Acne is caused by several factors. 

Hormones

During the teen years, rising levels of male hormones, such as testosterone (found in both males and females) stimulate the oil-producing glands in the skin to enlarge and secrete more oil. The excess oil combines with dead skin cells to plug skin pores. Acne spots begin to form.

Genes

There is a genetic component to acne. One study of teenage acne sufferers found 78% had a close family relative with the condition. More importantly, those with a family history of severe acne are more likely to get it at an earlier age and develop severe acne.

Medications

Acne can be caused by starting or stopping some prescription medications such as the contraceptive pill or other hormonal treatments, or by drugs such as prednisone, lithium and anabolic steroids.

Hormonal abnormalities

There is a greater risk for those with polycystic ovary syndrome (PCOS) or Cushing’s Syndrome.