What Causes Stretch Marks
Stretch marks happen when the skin is stretched for a prolonged period or when it happens rapidly. Of the three layers of skin; the epidermis, dermis and the subcutaneous stratum, it is the dermis that appears to be affected by the expansion. It is this region that helps skin retain elasticity.
The dermis contains concentrations of collagen and elastic fibers called elastin. When these substances and tissues are weakened, skin damage occurs. When rapid weight gain happens the resulting stretching seems to lead to tearing of underlying fibers and that results small rips and scarring.