Stretch marks are visible lines on the skin that form when the deeper layer of skin (the dermis) stretches faster than its structural fibers can keep up with. They’re extremely common, appearing in roughly 50 to 90% of women at some point in life and up to 86% of adolescents during growth spurts. In most cases, they’re a completely normal response to rapid changes in body size and carry no medical significance.
What Happens Inside the Skin
Your skin has three layers, and stretch marks originate in the middle one, the dermis. This layer contains collagen and elastin fibers that give skin its strength and bounce. When skin stretches rapidly, immune cells in the dermis release enzymes that break down elastin fibers in a process called elastolysis. The collagen bundles then reorganize, and the normal architecture of the dermis is disrupted. Think of it like pulling a knit sweater too quickly: the individual threads don’t snap cleanly, but the weave distorts and thins out in spots.
Hormones play a significant role in this process. Glucocorticoids, your body’s natural stress hormones (cortisol being the most well known), suppress the cells responsible for building new collagen and elastin. This is why stretch marks often appear during periods when these hormones are elevated, like pregnancy, puberty, or times of significant stress. It’s also why people using corticosteroid medications, whether as creams or pills, can develop stretch marks even without significant weight change. In those cases, the marks aren’t caused by skin tension at all but by the medication directly weakening the skin’s structural support.
Why They Change Color Over Time
Stretch marks go through two distinct stages, and the color tells you which stage you’re looking at.
In the early stage, the marks appear as reddish or purplish, slightly raised lines running perpendicular to the direction the skin is being pulled. The skin in the area may feel flattened, thin, or mildly itchy before these lines appear. At this point the dermis is swollen, blood vessels are visible through the thinned skin, and the tissue is actively remodeling. This is the stage where treatments are most effective, because the skin is still trying to repair itself.
Over months to years, the marks fade to white, silver, or flesh-colored and become flatter and less noticeable. At this point they resemble scar tissue: the top layer of skin thins out, collagen bundles pack densely and lie flat, and the elastic fiber network is largely gone. Mature stretch marks are permanent structural changes. They don’t disappear on their own, though they continue to fade and become less visible with time.
Common Causes and Risk Factors
Any situation that stretches the skin rapidly or weakens its support fibers can trigger stretch marks. The most common triggers include:
- Pregnancy: The abdomen, breasts, and hips expand quickly, especially in the third trimester, when cortisol levels are also naturally elevated.
- Puberty: Growth spurts cause rapid changes in height, hip width, or chest size. Boys often get them on the lower back and shoulders, girls on the hips, thighs, and breasts.
- Rapid weight gain or loss: This includes muscle gain from bodybuilding, not just fat.
- Corticosteroid use: Topical steroid creams applied for long periods, oral steroids, or conditions that raise cortisol levels internally all weaken the dermis.
Genetics matter more than most people realize. If your parents have stretch marks, you’re more likely to develop them. This comes down to inherited differences in skin elasticity, collagen density, and how your body handles the repair process. Certain genetic conditions like Marfan syndrome, which affects connective tissue throughout the body, carry a higher risk as well.
When Stretch Marks Signal Something Else
Most stretch marks are harmless, but certain characteristics can point to an underlying medical issue. Wide, deep purple or red stretch marks that are more than 1 centimeter across, particularly on the abdomen, may be a sign of Cushing syndrome, a condition in which the body produces too much cortisol. These marks look noticeably different from typical stretch marks: they’re darker, wider, and often appear alongside other symptoms like unexplained weight gain concentrated around the midsection, thinning skin that bruises easily, and muscle weakness.
If you develop prominent stretch marks without an obvious explanation (no recent pregnancy, growth spurt, weight change, or steroid use), that’s worth mentioning to a doctor, especially if you’re also experiencing fatigue or other new symptoms.
What Actually Works for Treatment
The honest answer is that no treatment fully erases stretch marks, but several can reduce their appearance, particularly when started early during the red or purple stage.
Prescription retinoid cream applied daily for several months has been shown to reduce the size of established stretch marks by stimulating collagen production. It works best on newer marks and cannot be used during pregnancy. Over-the-counter retinol products are weaker versions of the same compound and may offer modest improvement with consistent use.
Plant-based ingredients have also shown promise. Centella asiatica extract, often listed as “cica” or “tiger grass” in skincare products, has been studied for its ability to support skin repair. In laboratory and tissue studies, the extract boosted collagen production by 49% and elastin production by 37% in stretch-marked skin samples. It also reduced markers associated with scarring and tissue breakdown. These results come from controlled lab settings and may not translate directly to what you’d see in the mirror, but the ingredient has a reasonable evidence base compared to most cosmetic claims.
Professional procedures like laser therapy, microneedling, and chemical peels work by triggering the skin’s wound-healing response, encouraging new collagen formation in the damaged area. Multiple sessions are typically needed, and results vary depending on skin tone, mark severity, and how old the marks are. Older, white stretch marks are harder to treat because the tissue has already settled into its scar-like state.
For prevention, keeping the skin well-moisturized during pregnancy or periods of rapid growth won’t stop stretch marks from forming at the dermal level, but it supports skin flexibility and may reduce severity. Managing the rate of weight change, where possible, gives the skin more time to adapt.
Who Gets Them and Who Doesn’t
There’s a wide range in how people are affected. Some women go through pregnancy with no visible marks at all, while others develop extensive marks despite using every cream available. The variation is largely genetic. Skin color also plays a role in visibility: stretch marks are often more noticeable on darker skin tones during the early red stage and on lighter skin tones during the mature white stage, though this varies from person to person.
Age is a factor as well. Younger skin, somewhat counterintuitively, is more prone to stretch marks because it has higher elastin content that’s more susceptible to the enzymatic breakdown triggered by rapid stretching. This is one reason puberty is such a common time for stretch marks to appear, even in teens who are at a healthy weight and growing at a normal rate.