Blackheads, essentially open-air pimples, can appear on any part of your body and be especially frustrating to deal with.“They represent a tiny skin opening (pore) which is plugged at the surface of what is called the pilosebaceous unit. This plug made up of sebum (oil) and dirt, has an open pores expose to the air that causes it to look black, that is why it is called blackheads.But if the skin over the bump stays closed, the bump is called a whitehead.

Some factors can increase your chances of developing acne and blackheads, including:

http://www.healthmister.com/2017/09/blackheads-causes-prevention-and-treatment/