Acne Vulgaris is an inflammatory disease of the skin, caused by changes in the pilosebaceous units (skin structures consisting of a hair follicle and its associated sebaceous gland). Acne lesions are commonly referred to as pimples, spots, or "zits".

Acne develops as a result of blockages in follicles. Hyperkeratinization and formation of a plug of keratin and sebum (a microcomedo) is the earliest change. Enlargement of sebaceous glands and an increase in sebum production occur with increased androgen (DHEA-S) production at adrenarche. The microcomedo may enlarge to form an open comedo (blackhead) or closed comedo (whitehead). Increased sebum production provides an environment for the overgrowth of Propionibacterium acnes. Bacterial overgrowth of Propionibacterium acnes can cause inflammation, leading to inflammatory lesions (papules, pustules, or nodules) in the dermis around the microcomedo or comedo, which may result in scarring.[1]

Acne is most common during adolescence, affecting more than 85% of teenagers, and frequently continues into adulthood. [2] For most people, acne diminishes over time and tends to disappear, or at least decrease, after one reaches his or her early twenties. There is, however, no way to predict how long it will take for it to disappear entirely, and some individuals will continue to suffer from acne decades later, into their thirties and forties and even beyond.[3]

The most common form of acne is known as "acne vulgaris", meaning "common acne." Many teenagers get this type of acne.

The face and upper neck are the most commonly affected, but the chest, back and shoulders may have acne as well. The upper arms can also have acne, but lesions found there are often keratosis pilaris, not acne. The typical acne lesions are comedones and inflammatory papules, pustules, and nodules. Some of the large nodules were previously called "cysts" and the term nodulocystic has been used to describe severe cases of inflammatory acne. True cysts are rarely found in acne, and the term should be abandoned and the term severe nodular acne used instead.[4]

Aside from scarring, its main effects are psychological, such as reduced self-esteem[5] and, according to at least one study, depression or suicide.[6] Acne usually appears during adolescence, when people already tend to be most socially insecure. Early and aggressive treatment is therefore advocated to lessen the overall impact to individuals.[5]