The most common form of Acne is called Acne Vulgaris, which translates literally to "common acne". This is the type that can cause blackheads, papules, pustules, whiteheads, cysts and nodules.

Blackheads form in pores that are partially blocked. The substance that actually causes oily skin - called sebum - along with dead cells and bacteria slowly drain to the skin's surface. The black color occurs when the pigments in the skin are exposed to air. Blackheads can often take a long time to disappear.

Papules are small red-colored bumps on the skin's surface. They're usually tender to the touch and irritating, but it's important not to squeeze them or even touch them if possible. Squeezing them or touching them excessively can lead to aggravation and ultimately scarring.

Pustules are what is common known as pimples or "zits". They look like a red circle with a center that's yellow or white.

Whiteheads differ from blackheads in that they are contained underneath the skin's surface. These are caused by pores that are completely blocked, trapping the sebum, dead cells and bacteria beneath the surface of the skin.

Nodules are quite a bit bigger than most other forms of acne. They're hard lumps underneath the skin's surface, which are usually quite painful and can last for weeks or months. Nodules are very prone to causing scarring, so it is wise to see a dermatologist for treatment before the scarring can occur.

Cysts are very similar to nodules with the exception that they're filled with pus. Cysts are usually quite painful and will often lead to scarring if they're left untreated. As with nodules, it's best to see a dermatologist for treatment.