At puberty your body undergoes many hormonal changes, in particular, an increase in testosterone, (in girls as well as in boys). It is this sex hormone that causes your pimples: it is carried in your blood and spreads throughout your body, in particular, to your hair follicles (small "sacs" containing hair and sebaceous glands).

The testosterone stimulates your sebaceous glands a little too much and they begin to produce large amounts of sebum. This fatty substance is useful for your skin: it serves to protect and moisturise it. But when there is too much of it there is a problem! Your skin becomes oily and shiny and pimples begin to appear.

This phenomenon is very common among teenagers: 80% of teenagers between the ages of 11 and 18 years are affected by it. But do not despair: in most cases the acne disappears spontaneously when the hormones settle down between the ages of 18 and 20 years. In the meantime, go and see a dermatologist to get your acne treated!