system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is acne found more on the face/upper torso than elsewhere on the human body?

 Back/neck acne is quite common, but from there, finding additional patches become much more rare. Never quite knew why, but I am certain it must involve the frequent amount of hair follicles upon the upper torso. 

**Edit:** Thank you for the front page.
gpt
No one is completely sure exactly what causes acne, but we know some things that put you at higher risk.  

Acne is a disease of the glands that secrete sebum onto hair follicles, sebum is a waxy/oily substance that protects the skin.  These glands are most dense on the face.  Then hormones, especially "male hormones" (androgens) cause these glands to secrete even more, providing a nice oily, anaerobic (no oxygen) little bubble for the bacteria that causes acne to grow in. The glands that are most sensitive to these hormones are found in face/neck/chest/back, which is another reason why those are the sites of acne flares.