Why Do We Get Stretch Marks? The Science Behind It

Stretch marks are scars. That single fact explains most of what follows. When skin stretches faster than its supporting structures can adapt, the mesh of collagen and elastin underneath the surface tears, and the body repairs the damage with scar tissue rather than normal skin. The result is a streak that looks different from the skin around it — and, importantly, behaves differently too. They are extremely common. Most pregnant women develop them, and they show up in adolescence, during rapid growth, and with fast weight change in people of all body types.

The medical name is striae distensae. They are not a sign of poor health, weak skin, or bad habits. They are a normal response of skin pushed past its mechanical limits.

Why Do We Get Stretch Marks?

Stretch marks form when the dermis — the thick middle layer of skin — tears under tension it cannot keep up with. The dermis holds most of the skin’s collagen and elastin, the fibers that give it strength and the ability to snap back. When skin expands quickly, these fibers can rupture. The body then patches the area with scar tissue, which has less collagen, different fiber alignment, and fewer working elastic fibers than normal skin. That scar tissue is what you see through the surface.

Two things have to happen together. First, the skin has to be stretched — by pregnancy, growth, weight gain, or another cause. Second, the dermis has to be unable to adapt fast enough. Slow, gradual stretching usually gives skin time to remodel. Rapid stretching does not.

One detail people often miss: stretch marks are not simply “stretched skin.” The skin is genuinely damaged at the level of its structural proteins. That is why they don’t tan, don’t grow hair normally in some cases, and feel slightly different in texture. It also explains why they fade over time but rarely disappear completely.

What Actually Happens Inside the Skin?

The dermis is a scaffold. Collagen fibers provide tensile strength, and elastin fibers let skin return to shape after stretching. When tension exceeds what that scaffold can handle, individual fibers break. The body responds with inflammation and then a repair process that lays down new collagen — but not the organized, strong kind. The new tissue is disorganized and weaker.

This repair process happens in stages, and the visible appearance changes with them:

• Early stage (striae rubrae): Fresh marks look red, pink, or purple. This color comes from blood vessels in the healing tissue and active inflammation. During this phase the mark is still being actively remodeled.
• Later stage (striae albae): Over months to years, the redness fades and the mark becomes pale, silvery, or white, often slightly indented. The blood vessels recede and the scar tissue matures.

The shift from red to white matters practically. Marks in the early, red stage respond better to some treatments than older white ones, because the tissue is still active. Once a mark has turned white, the scar is largely mature and harder to change. This is one of the few areas where the timeline genuinely affects what is realistic to expect.

Who Gets Stretch Marks and Why?

Stretch marks are most common during pregnancy, puberty growth spurts, and rapid weight gain or loss. They also occur with certain medical conditions and long-term use of corticosteroid medications, which can weaken skin’s structural proteins. Each of these shares the same underlying trigger: fast change in skin tension combined with limited ability to adapt.

Some clear patterns:

• Pregnancy: The majority of pregnant women develop stretch marks, most often on the abdomen, breasts, and thighs as the body expands over months.
• Adolescence: Growth spurts can outpace skin adaptation, which is why stretch marks appear on the back, thighs, and hips during the teen years.
• Weight change: Rapid gain stretches skin quickly; rapid loss can leave loose skin and make existing marks more visible.
• Bodybuilding and rapid muscle growth: Fast increases in muscle size can stretch the overlying skin, particularly around the shoulders and arms.
• Medication-related: Long-term use of topical or systemic corticosteroids is associated with stretch marks, because these drugs can reduce collagen production and thin the skin.

Genetics also matter. Some people develop stretch marks easily and others barely at all under similar circumstances, which points to inherited differences in skin structure and collagen quality. The evidence for exactly which genes are involved is still limited.

Are Stretch Marks a Sign of a Health Problem?

For most people, no. Stretch marks on their own are a cosmetic and structural change, not a marker of disease. They are extremely common and usually harmless.

There are exceptions worth knowing. Stretch marks that appear suddenly, spread widely, or show up alongside other symptoms can sometimes be linked to an underlying condition — for example, Cushing’s syndrome, where excess cortisol weakens skin and can produce wide, dark stretch marks. Rapid, unexplained stretch marks with other signs such as easy bruising, muscle weakness, or weight changes around the trunk deserve a medical conversation. This is uncommon, but it is the reason sudden widespread marks are not something to dismiss automatically.

If stretch marks appear without an obvious cause like growth, pregnancy, or weight change, it is reasonable to ask a clinician about them.

Can Stretch Marks Be Prevented?

The honest position: there is no proven way to prevent stretch marks in everyone. The strongest evidence concerns risk factors, not prevention. Because rapid stretching and skin that cannot adapt fast enough are the core drivers, avoiding very fast weight change is the most reliable general step — but even that does not guarantee anything, and pregnancy-related stretching is largely unavoidable.

Many creams, oils, and lotions are marketed for prevention. The evidence that they prevent stretch marks is weak. Some studies have looked at specific ingredients, but results are inconsistent and no product has been shown to reliably prevent them across large trials. Moisturizing may help skin feel more comfortable and may support the skin barrier, but feeling better moisturized is not the same as preventing tears in the dermis. No cream reaches deep enough to rebuild torn collagen fibers.

This is a case where the marketing runs far ahead of the evidence. If a product claims to prevent stretch marks, treat that claim with skepticism.

Do Stretch Marks Ever Go Away?

They fade, but they rarely disappear completely. Over time the redness of early marks subsides and they become pale and less noticeable. Many people find they become far less visible with age, especially on areas usually covered by clothing.

Complete removal is not realistic with any current approach. A range of treatments — including topical retinoids, laser therapy, microneedling, and other procedures — has been studied for improving appearance. Some show modest benefit, particularly for early red marks, but results vary, none erases marks entirely, and outcomes differ from person to person. These are best discussed with a dermatologist, who can explain realistic expectations and risks for your specific skin and mark type. This article is informational and not a recommendation for any specific treatment.

One useful reframe: stretch marks are extremely common, and their presence says nothing about your health or habits. They are a record of change your skin went through, not a flaw to be fixed.