A stretch mark is a type of scar that develops when our skin stretches or shrinks  quickly due to loss or gain in volume. The abrupt change can causes the collagen and elastin to rupture and stretch marks may then appear as the skin heals. They usually begin as a purple/red thin band and they then develop to a silvery white colour. weight loss or weight gain, puberty, pregnancy all can result in stretch marks on the skin and they can be much improved if bothersome for the individual.