Acne vulgaris is a follicular disorder occurring in pilosebaceous units in the skin of the face, neck, and upper trunk. These sebaceous follicles have follicular channels and adjacent multiacinar sebaceous glands. In the lubrication process of normal skin, sebum travels through the follicular canal to the skin surface, carrying along with it desquamated cells from follicular epithelium. Acne develops when these specialized follicles undergo pathologic alterations that result in the formation of non-inflammatory lesions (comedones) and inflammatory lesions (papules, pustules, and nodules).