What causes acne?

As Johns Hopkins Medicine explains, acne is actually related to your hair follicles as well as your oil glands, which are also known as sebaceous glands. Your oil glands are there to secrete oils and moisten your skin. Normally, this oil travels through the hair follicles to the skin’s surface, but with acne, that doesn’t happen correctly, and skin cells block the follicles instead. This traps the oil (known as sebum), and bacteria starts to grow inside the plugged-up hair follicles. That process is what leads to the pimples and clogged pores that are commonly seen with acne.