Stretch marks is one of the most confusing beauty topics—and that might be because while they're very common, they're kind of unpredictable by nature.
First, we went to myth-bust how they really form. "To put it simply, a stretch mark is a scar of the deeper layers of the skin," explains dermatologist Dr. Rita Linkner. "These layers are the building blocks of the skin and where collagen and elastin work to keep the skin supple and elastic. If these basic proteins are shifted, then linear scars form."
They're are also two different types of stretch marks. At first, they might seem inflamed or red in color, and Linkner says these are called striae rubra. Then, over time, they usually turn white and are given the name striae alba.
So the why? There's a few different factors that can come into play.
"They can occur from rapid changes in weight. They can happen during growth spurts in young women and men," says Dr. Bruce Katz, Founder and Director of the Juva Skin & Laser Center. "They can also occur when people are on high doses of steroids for medical problems, so that’s typically the way they develop."
While Dr. Katz says there isn't a specific gene associated with the formation of stretch marks, he does say they tend to run in families and there can be a predisposition in their formation.
But according to cosmetic dermatologist Dr. Paul Jarrod Frank, there's another genetic component that could play into stretch marks.
"Some people have more thicker or thinner skin than others," Frank says. "While there are susceptibilities to it, it’s also a matter of nature versus nurture. You can have the most elastic skin in the world, but if you have a set of twins, you have a lot more propensity for stretch marks."
As for treatments, there's products like Bio Oil ($10; target.com), various moisturizers that strengthen the skin's ability to stretch, and several in-office procedures that can erase them completely.