Girls typically start to get acne when their hormones kick in (approximately 11 to 13 years old), which is about the time that they start their period.Boys start to get acne at the age of approximately 12 years, with a range of 9 to 15 years old.As most girls will attest, boys on average mature later than girls. Early on in the onset of teen acne, the main lesions are blackheads and whiteheads. Later in puberty, there is a higher incidence of inflammatory lesions.irls typically start to get acne when their hormones kick in (approximately 11 to 13 years old), which is about the time that they start their period.