What is acne vulgaris?

Acne vulgaris is the medical term for the most common type of acne. Acne vulgaris develops when sebaceous glands in the skin make too much sebum, the oily substance that lubricates the skin and hair. This oil can clog pores, where bacteria can thrive. The immune system fights back, causing oil-filled pores to become red, swollen pimples. Acne vulgaris often occurs during puberty, when hormones surge, and other situations in which hormones are out of balance. This type of acne tends to run in families.