Blackheads are small bumps that appear on your skin due to clogged hair follicles. These bumps are called “blackheads” because the surface looks dark or black. Blackheads are a mild type of acne that usually form on the face, but they can also appear on the back, chest, neck, arms, and shoulders. Acne affects 40 to 50 million Americans and is the most common skin disorder in the United States.