Acne affects 95% around 95% of people between the ages of 11 and 30 years to some extent. It usually disappears in the mid-20s but 3% of people still have symptoms beyond 35 years. It most commonly develops on the face but 50% of sufferers have lesions on their backs and 15% on their chest as well.
This is a chapter from Breastfeeding and Chronic Medical Conditions still available on Amazon as a paperback or download.
For factsheet on acne see https://breastfeeding-and-medication.co.uk/wp-content/uploads/2022/06/acne-vulgaris.doc.pdf