Acne vulgaris (commonly called acne) is a skin disease caused by changes in the pilosebaceous units (skin structures consisting of a hair follicle and its associated sebaceous gland). Severe acne is inflammatory, but acne can also manifest in noninflammatory forms.eMedicine - Acne Vulgaris : Article by Julie C Harper 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.

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. Anderson, Laurence. 2006. Looking Good, the Australian guide to skin care, cosmetic medicine and cosmetic surgery. AMPCo. Sydney. ISBN 0 85557 044 X.

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.

Aside from scarring, its main effects are psychological, such as reduced self-esteem and, according to at least one study, depression or suicide.One study has estimated the incidence of suicidal ideation in patients with acne as 7.1% :* 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.

Cystic acne, also known as nodulocystic acne, is a severe form of acne wherein acne develops into small cysts. Acne cysts are not true cysts in the sense that they are not abnormal dilations of skin structure, but rather nodules of inflammation. Although not uncommon, it is rarer than other types of acne. Like other forms, it is caused by an excess buildup of sebum in the pores and, contrary to popular belief, is not caused by, nor is it affected by, hygiene or the lack thereof. A common treatment for cystic acne is Isotretinoin, which cures most acne in about 90% of patients.

Cystic acne can affect the face, chest, back, shoulders and, occasionally, upper arms. Like pimples, which are more common, cysts are usually filled with a white pus-like substance. They are usually several millimeters in diameter, and can be quite painful.

If cystic acne is not treated early on, especially with antibiotics along with a topical cream, some degree of scarring will occur. This can be quite severe depending on the case. Although many scars can be treated, scars on the body often do not respond as well as those on the face. In most cases, it is unlikely that all scars can be removed. After cysts have mostly healed, macules, or "pseudo scars" may form. Macules are red patches of skin, sometimes raised slightly, where cysts used to be, and may resemble cysts in their appearance. They are sometimes known as "pseudo scars" because they resemble scars, but unlike true ones, macules usually only last up to six months and leave no permanent scar.

A pimple is a result of a blockage of the skin's pore. It can be a pustule or papule.