Stretch marks are a type of scar that occurs when the skin stretches rapidly. Examples include: growth spurts during puberty, pregnancy, rapid weight loss or gain, and bodybuilding. It can appear as pinkish, purplish, or flesh colored linear bands or streaks on the skin that are depressed or indented. Common sites of involvement include arms (near the armpits), medial thighs (near the groin), abdomen, breasts, hips, and buttocks. Stretch marks do not require treatment and often fade and become less noticeable over time, even without any intervention.