Definition of Stretch Marks

Stretch marks are a type of scar that develops when skin stretches quickly. Stretch marks are caused by damage to collagen and elastin fibers in the skin that occurs due to rapid growth. Early stretch marks can be red, purple, pink, or brown. They often fade over time and may leave a slight depression. Stretch marks are not harmful or painful, but many people do not like the appearance, and they are permanent, like all scars. Conditions that can cause stretch marks include pregnancy, weight gain in obesity, growth spurts in teenagers, medication side effects, or a rapid increase in muscle size through weightlifting.