Acne is classified into three for treatment purposes: comedonal, inflammatory and nodulocystic.

Comedonal acne is also commonly known as whitehead or blackhead. Whiteheads are closed comedones, or trapped sebum. Blackheads are open comedones, giving it a dark color.

Inflammatory acne occurs when the bacteria present in trapped sebum (Propionibacterium acnes) produces enzymes that stimulate the inflammatory process. The skin ruptures and yellow substance appears as pus, but are actually excess sebum. Topical creams and antibiotics may treat inflammations.

Nodulocystic acne consist of comedones and inflammatory lesions and deeper nodules and cysts. This needs oral antibiotics, since it will no longer be treated by topical creams.

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