There are many different types of acne. Although the cause of almost all of them is the same — a clogged pore — they come in many shapes, colors and sizes. The most common types include: Whiteheads – Whiteheads happen when pores are clogged all the way through. Due to the full congestion of the pore, they are known as closed comedones. Blackheads – Unlike whiteheads, blackheads have a dark appearance on the skin’s surface. Because the head of the pore remains open while the rest of the pore is clogged, they are known as open comedones. Papules – When oil or excess skin cells block a pore and mix with bacteria on your skin, small red bumps can form known as papules. Pustules – A pustule is a small, bulging bump with red, inflamed skin surrounding a white center.  Nodules – Nodular acne consists of red or flesh-colored bumps that are deep within the skin’s surface. Nodular acne is usually a result of a bacterial infection caused by C. acnes and causes a painful infection deep within the pore. Cysts – The most severe form of acne is cystic acne. It is often the result of an infection deep within the skin. Acne cysts are painful, red, inflamed and filled with pus. Because they are pus-filled, cysts are softer than nodules. They often burst, infecting the surrounding skin.