What Creates Stretch Marks?

Stretch marks are scars. They form when skin stretches faster than its middle layer can rebuild itself, tearing the collagen and elastin fibers that keep skin firm. The body patches the damage with scar tissue, which shows up as the streaks most people call stretch marks.

That is the short, accurate answer. The longer story involves hormones, genetics, growth spurts, weight change, and pregnancy. It also involves a lot of products that promise to erase them and mostly do not. Here is what the evidence actually supports.

What Creates Stretch Marks in the Skin?

The dermis is the layer that matters. It sits beneath the surface and holds most of your skin’s collagen and elastin, the proteins that let skin stretch and snap back. When the dermis is pulled faster than it can produce new fibers, some of those fibers break.

The body responds the way it responds to any wound: it lays down scar tissue. That scar tissue is less elastic and reflects light differently from normal skin, which is why stretch marks look like lines or bands rather than smooth skin.

Two things have to happen together for this to occur. The skin has to be under real mechanical tension, and the dermis has to be unable to keep pace. Slow, gradual stretching usually gives the dermis time to adapt. Rapid stretching does not.

The medical term for stretch marks is striae distensae. You may also see them called striae gravidarum when they happen during pregnancy.

What Causes Stretch Marks Besides Stretching?

Mechanical stretch is the trigger, but hormones and genetics decide how vulnerable your skin is. This is why two people can gain the same amount of weight and only one develops marks.

Glucocorticoids are the key hormonal players. These are steroid hormones the body makes naturally, and they also come in medication form. They reduce collagen and elastin production in the skin and weaken the fibers that are already there. That is why stretch marks are a known side effect of prolonged use of corticosteroid medications, both topical and systemic.

This hormonal effect also explains why stretch marks appear in situations where stretching alone does not fully account for them. They show up during puberty, during pregnancy, and in some people who take anabolic steroids. In each case, hormones are changing the skin’s ability to handle tension at the same time the skin is being stretched.

Genetics matter too. If a close family member has stretch marks, your own risk is higher. The specific genes involved are not fully mapped, but the pattern is consistent enough that researchers treat family history as a real factor.

Who Gets Stretch Marks Most Often?

Certain life stages and conditions make stretch marks far more common. The underlying theme is rapid change combined with shifting hormones.

• Pregnancy. A large share of pregnant women develop stretch marks, most often on the belly, breasts, hips, and thighs. They usually appear in the later trimesters as the abdomen expands.
• Puberty. Growth spurts during adolescence stretch skin quickly. Marks commonly appear on the thighs, hips, breasts, and back.
• Rapid weight gain. Fast increases in body weight stretch the skin before the dermis can adapt.
• Rapid muscle growth. Bodybuilders, particularly those using anabolic steroids, can develop marks on the shoulders, chest, and arms.
• Corticosteroid use. Long-term use of steroid medications raises the risk.
• Certain medical conditions. Conditions that affect connective tissue or hormone levels can make stretch marks more likely.

Stretch marks affect men and women. They are simply more common in women, largely because of pregnancy and differences in how fat and skin are distributed.

Why Do Stretch Marks Change Color Over Time?

A fresh stretch mark and an old one are at different stages of the same scar. The color shift is a normal part of how the tissue heals and remodels.

New stretch marks often look red, purple, or pink. This stage is called striae rubrae. The color comes from inflammation and from blood vessels in the healing tissue. During this phase the mark is still active, and it is the period when treatment has the best chance of making a difference.

Over months to years, the mark fades to a silvery or white tone. This stage is called striae albae. The redness goes away because the inflammation settles and the blood vessels recede. What remains is mature scar tissue. Once a stretch mark reaches this stage, it is generally considered permanent — the color fades, but the texture and the slight indentation usually do not go away.

Do Any Treatments Actually Work?

This is where honesty matters most, because the gap between marketing and evidence is wide. No product has been shown to erase mature stretch marks. Some treatments show modest improvement, mostly when used early.

For fresh, red stretch marks, some evidence suggests certain topical ingredients may help. Research on topical retinoids, particularly tretinoin, has shown some improvement in the appearance of early stretch marks in small studies. This is a prescription medication, and it is not considered safe during pregnancy. Some studies also suggest centella asiatica extract and hyaluronic acid preparations may offer modest benefit on new marks. The word to hold onto is “modest.”

For mature, white stretch marks, the evidence is weaker. Laser therapy and microneedling are used by some dermatologists and have shown some improvement in texture and color in clinical studies, but results vary and multiple sessions are typically needed. These are procedures, not creams, and they are performed in a clinical setting.

What does not have good supporting evidence: most over-the-counter stretch mark creams and oils sold specifically for this purpose. Many contain cocoa butter, vitamin E, or plant oils. Studies testing these on stretch marks during pregnancy have generally not found them better than a placebo or no treatment. They may feel good on the skin. That is not the same as changing the scar.

One practical point: timing matters more than brand. Treatments are more likely to help a red, recent mark than a white, old one. If a product claims to remove old stretch marks entirely, that claim is not supported by clinical evidence.

Can You Prevent Stretch Marks?

You cannot fully prevent them, because you cannot control the genetics and hormones that set your risk. You can lower the odds in some situations by keeping weight change gradual rather than sudden.

During pregnancy, steady, appropriate weight gain guided by a clinician is the most reasonable step. Rapid gain stretches skin faster. Beyond that, the evidence for prevention is thin. Studies on massage, oils, and creams for preventing stretch marks during pregnancy have not shown reliable benefit.

If you take corticosteroid medication long term, that is a conversation to have with your prescriber about risks and monitoring. Do not stop a prescribed medication on your own.

For most people, the honest summary is this: stretch marks are common, they are not a sign of poor health, and they are not dangerous. They are scar tissue doing what scar tissue does.