Stretch marks are a type of scarring under the skin that appears when skin stretches rapidly, such as during pregnancy. This rapid change prompts the collagen and elastin in your skin to rupture, causing stretch marks to appear. Initially, they “have a purple, pink, or red hue, gradually fading to more of a skin-toned color,” Dr. Badreshia-Bansal says. While there are several potential factors that may contribute to the appearance of stretch marks, a 2013 study suggests that stretch marks may be due to genetic factors. This means that some people are more prone to getting stretch marks than others simply based on their genetics. This is important to keep in mind when trying to reduce the appearance of your stretch marks, as you may be more prone to getting darker or more stretch marks simply because of your genetics, which is totally normal.