Blackheads look like black dots that have formed on your skin. Blackheads are called open comedones. Comedones are the skin-colored bumps that form when you have a pimple. In the case of blackheads, these comedones consist of follicles beneath your skin with very large openings, or pores.
When you have blackheads, these large pores become clogged with a substance known as sebum. A chemical reaction with the sebum occurs under your skin. Melanin is oxidized and turns the clogged pores a black color. This form of acne is often found on your back, shoulders, and face.
Whiteheads are known as closed comedones. The follicles beneath your skin become filled with bacteria and have a very small opening at the top of your skin. Air isn’t able to enter the follicle. The bacteria inside of it doesn’t undergo a chemical reaction, so it stays white in color. This type of acne is also found on your back, shoulders, and face.