Acne is a general term that describes a variety of different types of pimples, blackheads, pustules, whiteheads and cysts.
Cystic acne are nodules that are red, raised, often 2–4 mm in size and nodular and are the most severe form of acne.
You get a pimple when a pore in your skin gets clogged, usually with dead skin cells. Sometimes bacteria get trapped inside the pore, too, causing the area to become red and swollen.
Cystic acne happens when this infection goes deep into your skin, creating a red, tender bump that’s full of pus. It may hurt or itch. If a cyst bursts, the infection can spread, causing more breakouts.