What is Acne?

Acne vulgaris (commonly called acne) is a skin disease caused by changes in the pilosebaceous units (skin structures consisting of a hair follice and its associated sebaceous gland). Severe acne is inflammatory, but acne can also manifest in noninflammatory forms.^[1] Acne lesions are commonly referred to as pimples, spots, or zits.

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 the very least decrease—after one reaches his or her early twenties. There is, however, no way to predict how long it will take to disappear entirely, and some individuals will continue to suffer well into their thirties, forties and beyond.^[3]

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. Typical acne lesions are comedones, 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. ^[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 by some to lessen the overall impact to individuals.

Source : http://en.wikipedia.org