What Causes Stretch Marks? The Science of Striae
Stretch marks are one of the most common things skin does — and one of the most needlessly worried about. They're the streaked lines that appear when skin stretches faster than it can adapt, and they turn up on almost everyone at some point: through puberty, pregnancy, or any quick change in size. Here's what's actually happening in the skin, and what the evidence really says about them.
Stretch marks — known medically as striae distensae — are streak-like marks that form when the skin is stretched quickly and the collagen and elastin fibres in the dermis (the skin's deeper, structural layer) are disrupted. They start as red or purple lines (striae rubrae) and fade over time to pale, silvery ones (striae albae). They're extremely common, entirely harmless, and a normal feature of skin — not a scar you did something wrong to earn.
Stretch marks form when skin stretches faster than the dermis can keep up — during growth spurts, pregnancy, or rapid changes in weight or muscle. This disrupts collagen and elastin, leaving visible streaks. Hormones (especially cortisol) and genetics influence who gets them. They begin red/purple, then fade to white. Up to 90% of pregnancies involve them. They're harmless and very common — and honestly, no cream reliably prevents them and mature white marks are permanent. They're a normal part of a body that changes.
Skin has a built-in stretchiness, thanks to a mesh of collagen (strength) and elastin (spring) in the dermis. It can flex a great deal — but when it's stretched too far, too fast, that mesh can tear at a microscopic level. The skin heals, but the repaired area looks and behaves a little differently, and we see that as a stretch mark. Most commonly they show on the thighs, abdomen, hips, buttocks, breasts, lower back and upper arms.
What Are Stretch Marks?
A stretch mark is essentially a small, healed area of disrupted dermis. When skin stretches beyond what its collagen and elastin can accommodate, those fibres are pulled apart and reorganised. The overlying skin can look thinner, streaked and slightly different in texture or colour from the skin around it. Despite looking like scars, they cause no harm and carry no health risk at all.
They're usually described in two stages depending on their age, and that distinction matters — because it's the single biggest factor in whether anything can change how they look.
The Two Stages: Red Then White
| Stage | Look & feel | What's happening |
|---|---|---|
| Striae rubrae (early) | Red, pink or purple; may be slightly raised, and can itch | An early, inflammatory phase — small blood vessels in the disrupted dermis are visible through the skin. This is when marks are most responsive to any intervention. |
| Striae albae (mature) | Pale, silvery-white; flat, sometimes slightly sunken | The healed, settled phase. The redness has faded and the tissue has stabilised. At this point the marks are considered permanent. |
Why Do Stretch Marks Form?
Three main factors interact — and it's rarely just one of them:
1. Rapid stretching of the skin
This is the headline cause. Any time the body changes size quickly — a growth spurt in adolescence, pregnancy, or a fast change in weight or muscle mass — the skin is put under high mechanical tension. If that outpaces the dermis's ability to adapt, collagen and elastin fibres are disrupted and stretch marks appear.
2. Hormones
Hormones change how resilient skin is. In particular, high levels of cortisol — the stress hormone, also elevated in pregnancy and in certain medical conditions — are associated with reduced collagen production, which can make skin more prone to striae. (This is also why long-term use of potent steroid creams or oral steroids is a recognised trigger.) At a cellular level, excess cortisol appears to dampen signals such as TGF-β1 that normally prompt fibroblasts to build collagen.
3. Genetics
Family history matters. Some people simply have skin that's more prone to stretch marks — influenced by inherited differences in skin thickness and in how much collagen and elastin the skin produces. Skin thickness is also part of why, on average, men tend to get fewer stretch marks than women — though plenty of men still get them, especially with rapid growth or muscle gain.
Stretch marks aren't caused by "not moisturising enough." They form in the deeper dermis in response to stretching, hormones and genetics — not because of anything you did or didn't put on the surface. Moisturiser can keep skin comfortable, but it doesn't reinforce the dermis against these forces.
Who Gets Stretch Marks?
Almost everyone, at some point. The most common life stages and triggers include:
- Puberty — rapid growth spurts stretch the skin quickly (very common in teenagers of all genders).
- Pregnancy — striae gravidarum affect up to 90% of pregnancies.
- Rapid changes in weight or muscle — including significant muscle gain from training.
- Steroid use — prolonged potent topical or oral corticosteroids.
- Certain medical conditions — some conditions that raise cortisol are associated with striae.
Can You Prevent or Treat Stretch Marks?
Evidence-BasedThis is where honesty matters most, because the category is full of over-promising. Here's what the evidence actually supports:
- Prevention: no topical product reliably prevents stretch marks. Reviews of the research find only limited, weak evidence for a few ingredients, and several well-designed studies show creams and oils don't prevent them. Massage may play a small role, but expectations should be modest.
- Early (red) marks: respond better to intervention than mature ones. Some prescription and in-clinic options exist, but these should be assessed and carried out by a dermatologist.
- Mature (white) marks: are permanent. Their appearance can sometimes be softened by professional procedures, but they can't be erased — and they naturally become less noticeable over time on their own.
Stretch marks form in the dermis, but creams act mainly on the epidermis at the surface. That gap is an anatomical reality, not a formulation failure — it's why no topical, however elegant, can physically rebuild the deeper structure. If you're considering treatment for early marks, a dermatologist can talk you through options suited to your skin.
Are Stretch Marks Normal?
Completely. They're one of the most common features of human skin — a visible record of a body that grew, carried a pregnancy, gained strength, or simply changed. They're harmless, they fade with time, and they don't need treating unless you want to explore options. A great deal of the distress around stretch marks comes from marketing that sells them as flaws; the science frames them as ordinary.
We won't sell you a "stretch mark eraser," because no such thing exists. Mature stretch marks are permanent, no cream prevents them reliably, and we'd rather you knew that than spent money on a promise the biology can't keep. Stretch marks are normal — understanding them is more useful than fighting them.
Frequently Asked Questions
What actually causes stretch marks?
Skin stretching faster than the dermis can adapt — during growth, pregnancy or rapid weight/muscle change — which disrupts collagen and elastin. Hormones (especially cortisol) and genetics influence how prone you are.
Why do they start red and turn white?
Fresh marks (striae rubrae) look red or purple because blood vessels show through disrupted tissue in an early inflammatory phase. Over months they mature into flat, silvery striae albae. Early marks respond better to intervention; white marks are permanent.
Can any cream prevent or remove stretch marks?
No cream reliably prevents them, and mature marks can't be erased. The evidence for topicals is limited. Some in-clinic options can improve the look of early marks, and marks fade naturally over time. Creams act on the surface; stretch marks form deeper in the dermis.
Are stretch marks dangerous?
No. They're harmless and extremely common — up to 90% of pregnancies and most people at some point — and are a normal feature of skin, not a medical problem.
Why do women get more stretch marks than men?
Partly because men's skin tends to be somewhat thicker, and because women experience more common triggers such as pregnancy and puberty growth. Genetics and skin thickness both play a role — and plenty of men get them too.
Boldpurity Science Team
Boldpurity is a clinical skincare brand with in-house cGMP manufacturing in Hyderabad, India. Content is prepared and science-reviewed by the Boldpurity Science Team.
Editorial Process
Articles are drafted from peer-reviewed dermatology literature, science-reviewed for accuracy, and kept at an appearance-and-education level. We do not present cosmetic products as treatments for medical conditions or body concerns.
Reference Policy
Claims are supported by cited, verifiable sources (see References). Where the evidence is limited — as with stretch-mark prevention — we say so plainly rather than overstate it.
Medical Disclaimer
This article is general information, not medical advice. For treatment of stretch marks, or if you're pregnant and considering any topical or procedure, consult a qualified dermatologist or physician. Some prescription actives are unsuitable during pregnancy.
Stretch marks are a normal, harmless feature of skin. This article is educational and makes no promise to prevent, reduce or remove them. Any treatment decisions — especially during pregnancy — should be made with a qualified professional.
- Korgavkar K, Wang F. Stretch marks during pregnancy: a review of topical prevention. Br J Dermatol. 2015;172(3):606–615.
- Al-Himdani S, Ud-Din S, Gilmore S, Bayat A. Striae distensae: a comprehensive review and evidence-based evaluation of prophylaxis and treatment. Br J Dermatol. 2014;170(3):527–547.
- Ud-Din S, McGeorge D, Bayat A. Topical management of striae distensae (stretch marks): prevention and therapy of striae rubrae and albae. J Eur Acad Dermatol Venereol. 2016;30(2):211–222.
- DermNet. Striae (stretch marks). dermnetnz.org.
