For women...
there are
generally two periods in your life when
you grow rapidly. The first is puberty
and the second is
pregnancy.
During puberty you grow quickly both
in height and weight and stretch marks
are very common for both sexes. The
skin contains a protein called collegen
that is responsible for the elasticity
of the skin. The hormones of puberty
can disrupt the production of collagen
which leaves the skin in a state where
it is likely to
tear if it
undergoes rapid growth. This does
leave you prone to stretch
marks.
The bright red appearance of new
stretch marks can be distrssing. There
are creams that claim to be able to
reduce the stretch marks if treated
quickly. Given enough time they will
naturally fade in colour, though they
will not disappear completely.
The hormones of puberty can disrupt
the production of collagen which leaves
you prone to stretch marks.