The only way to make facial hair grow faster in teens is to increase the amount of testosterone in their body. The rate at which facial hair grows is directly related to the individual's amount of the male sex hormone testosterone. Once a boy enters puberty, his testicles produce more testosterone, which causes facial hair to grow dark and thick.
Girls actually grow facial hair as well. However, the facial hair on girls grows lighter and thinner because of the small amount of testosterone that they have in their bodies. Just as some men produce more testosterone than others, some women do as well. Facial hair on these women is sometimes more noticeable as a result.
Despite popular belief, shaving does not cause facial hair to grow back faster or thicker. This was brought to light by a study released in 1928 by Anatomical Record. Shaving simply causes facial hair to look thicker because shaving causes a flat end to be formed on the end of the hair. This flat end is much thicker than the fine point that hair normally forms. Although the flat end of one piece of hair is not noticeable, the flat end of hundreds of pieces gives facial hair a thicker, more fuller appearance.