Acne Wiki

Acne vulgaris (commonly called acne) is a common human skin disease, characterized by areas of skin with multiple noninflammatory follicular papules or comedones and by inflammatory papules, pustules, and nodules in its more severe forms. Acne vulgaris mostly affects the areas of skin with the densest population of sebaceous follicles; these areas include the face, the upper part of the chest, and the back. Severe acne is inflammatory, but acne can also manifest in noninflammatory forms.[ 1&lt;span /&gt;] Acne lesions are commonly referred to as pimples, blemishes, spots, zits, or simply acne. Acne lesions are caused by changes in pilosebaceous units, skin structures consisting of a hair follicle and its associated sebaceous gland, changes which require androgen stimulation.

Source: http://en.wikipedia.org/wiki/Acne