The exact reasons behind acne are unknown but it is believed that many factors contribute to the development of acne. The most important factor is the increase in the hormone level. The androgens which increase during puberty, make the sebaceous glands to enlarge and produce more sebum. Heredity factors are also behind the development of acne.

Some of the other factors that can contribute are greasy cosmetics and some medicines that can cause acne. Continuous friction against the skin by objects like helmet or a back pack or even a tight collar can also contribute to acne. Environmental factors like pollution and humidity also contributes to it.