Acne or pimples as they are commonly known as are caused primarily due to hormonal changes during puberty.85%people develop acne. The sebaceous glands secrete excess sebum under the influence of hormones and block the pores leading to open and closed comedones .infection by bacteria cause pustules and cysts which result in scar formation and pigmentation. Severity of acne is determined by genetic factors, hormonal changes, use of oil based cosmetics, scrubs and certain drugs especially steroids. High glycemic diet is implicated in the causation of acne. Treatment depends on grade of acne and underlying problem which is best decided by a dermatologist.