Stretch marks form when your skin stretches or shrinks faster than the underlying tissue can adapt. This rapid change causes collagen and elastin fibers in the middle layer of your skin (the dermis) to break apart, leaving behind linear scars visible on the surface. Pregnancy, growth spurts, rapid weight changes, muscle gain, and certain medications can all trigger them.
What Happens Inside Your Skin
Your skin has three layers, and stretch marks originate in the middle one. When skin is pulled taut quickly, immune cells in the dermis release enzymes that break down elastic fibers. This process, called elastolysis, weakens the structural scaffolding that normally lets skin snap back into shape. Collagen and another structural protein called fibrillin then reorganize in a disorganized pattern, forming scar tissue rather than healthy, flexible skin.
Fresh stretch marks (striae rubrae) look red, pink, or purple because inflammation and blood vessels are still visible through the thinned skin. Over months to years, blood flow decreases and the marks fade to white or silvery (striae albae). At that point, the scar is mature. The color change reflects healing, not disappearance: the altered collagen structure remains permanently unless treated. Genetic research has also found that variations in genes controlling elastic microfibrils make some people inherently more prone to stretch marks than others, which is why two people can go through the same body changes with very different results.
Pregnancy
Pregnancy is the single most common cause. In a study of first pregnancies published in the Journal of the American Academy of Dermatology, 56% of women developed stretch marks. They typically appear on the abdomen, breasts, hips, and thighs during the second and third trimesters as the belly expands rapidly.
Age is the strongest predictor. Among pregnant women under 20, 84% developed stretch marks, compared with just 24% of women over 30. This likely reflects differences in skin elasticity and collagen density, both of which naturally change with age. Higher pre-pregnancy body weight and BMI also increase the odds, with each additional BMI point raising the risk by about 25%. Family history matters too: if your mother got stretch marks during pregnancy, your chances go up significantly.
Growth Spurts During Puberty
Teenagers commonly develop stretch marks during puberty, and it catches many families off guard. When bones lengthen quickly and the body adds weight over a short period, the skin over certain areas simply can’t keep pace. In teens, stretch marks most often show up on the abdomen, chest, hips, lower back, and thighs. Boys tend to get them on the back and shoulders, while girls more commonly see them on the hips and thighs.
These marks are entirely normal and don’t indicate a health problem. They often fade considerably over a few years as growth stabilizes and the skin continues to mature.
Rapid Muscle Gain
Bodybuilders and people who lift weights intensely can develop stretch marks when muscle volume increases faster than the overlying skin can stretch. The biceps, shoulders, and chest are the most common sites because those muscle groups tend to grow the fastest during strength training programs. Men are particularly prone to stretch marks on the upper arms and shoulders for this reason.
The mechanism is the same as any other cause: the skin’s elastic fibers tear under mechanical stress. Slower, more gradual muscle gain gives skin more time to adapt, though genetics still play a large role in whether marks appear at all.
Weight Fluctuations
Both rapid weight gain and the skin changes that follow significant weight loss can produce stretch marks. Gaining a large amount of weight over weeks or months stretches skin beyond its elastic limit, especially around the abdomen, flanks, and upper arms. Yo-yo dieting, where weight repeatedly cycles up and down, compounds the problem because the skin’s collagen fibers are damaged and repaired in a weaker configuration each time.
Corticosteroids and Medications
Long-term use of corticosteroid creams, lotions, or pills is a well-documented cause of stretch marks. Corticosteroids reduce the skin’s ability to produce collagen, making it thinner and less resilient. Even topical steroid creams applied to the same area for extended periods can cause localized skin thinning and stretch marks. One clinical case documented a patient who developed visible stretch marks on her forearm after using a high-potency steroid cream on the same spot for over two years.
Systemic corticosteroids (oral or injected) carry a higher risk because they affect skin throughout the body. If you use prescription steroid creams regularly, applying them for the shortest effective duration helps reduce this side effect.
Medical Conditions That Cause Stretch Marks
Certain health conditions produce stretch marks as a symptom, sometimes in patterns that look different from typical ones. Cushing’s syndrome, a condition where the body produces too much cortisol, causes distinctive pink or purple stretch marks on the stomach, hips, thighs, breasts, and underarms. These marks tend to be wider and more deeply colored than ordinary stretch marks. Cushing’s syndrome also causes a rounded face and a fatty hump between the shoulders, so stretch marks appearing alongside those features warrant a medical evaluation.
Connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome also increase susceptibility. People with these conditions have structural differences in their collagen or elastin from birth, meaning their skin is more fragile and prone to tearing even with normal growth.
Who Is Most at Risk
- Women are affected more often than men, partly because of pregnancy but also because of hormonal differences in skin composition.
- Younger people develop them more readily during periods of rapid change, as the data on pregnant women under 20 clearly shows.
- People with a family history of stretch marks are significantly more likely to get them, pointing to a strong genetic component.
- Those with higher body weight before a period of rapid change face increased odds.
Can You Prevent or Treat Them
No cream or oil has been proven to reliably prevent stretch marks. Keeping skin well-moisturized may improve its flexibility, but it won’t override genetics or the mechanical forces involved in rapid stretching. Gradual weight changes, when possible, give skin more time to adapt.
For marks that have already formed, the timing of treatment matters. Fresh, red or purple stretch marks respond better than old, white ones. Tretinoin cream (a prescription retinoid) applied daily for 12 weeks has been shown to reduce the length of pregnancy-related stretch marks by about 20%. Platelet-rich plasma injections performed by dermatologists have shown stronger results in clinical trials, with improvement and satisfaction rates near 87% to 90%, compared with about 60% for tretinoin cream alone.
Laser treatments, particularly fractional lasers, work by stimulating new collagen production in the scarred dermis. Multiple sessions are typically needed, and results vary depending on skin tone, mark age, and severity. Older, white stretch marks are the hardest to improve because the scar tissue is fully mature, though laser therapy can still reduce their visibility. No treatment eliminates stretch marks completely, but the combination of early intervention and professional procedures offers the most noticeable improvement.