A hard to remove acne or what called stone acne sometime is a problem for some people with particular type of skin. Acne is different from comedo. A comedo is a sebaceous follicle plugged with sebum. It is commonly called a blackhead. However, a stone acne is a harden acne that hard to be cured because it keeps on harden no matter what treatment it got.
Some people call these acnes as dark circles. Regardless of the race and ethnicity, all teenagers between 12 and 17 are commonly have acne.