When do guys get pit hair?

The development of pubic and axillary (underarm) hair is a secondary sexual characteristic that occurs during puberty in males and females. In males, the growth of chest and facial hair can also occur. These changes are caused by an increase in the production of testosterone, a hormone produced in the testes. The onset and progression of puberty can vary from person to person, but typically occurs between the ages of 12 and 16 for males.