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Stretch marks are an all too common occurrence, appearing on both men and women and most often occur on the chest, belly, thighs, and hips. But what causes stretch marks, and why do some people have more than others? This can be a confusing issue to tackle, but we’re here to help make it a little easier. This post will take a deep dive into the science behind stretch marks and their formation, from their root causes to the best treatments for reducing their visibility. We’ll also discuss the differences between atrophic and hypertrophic stretch marks and the various stages of the stretch mark formation process. We’re here to shed some light on the causes of stretch marks and provide you with helpful solutions.
What are Stretch Marks?
Stretch marks, also known as striae, are formed when the skin is stretched due to rapid growth or weight changes. They often appear in the abdomen, breasts, thighs, buttocks, and upper arms. When the skin is stretched, it weakens and small tears form inside the layers of the skin that produce a reddish or purplish mark on the surface. As the skin heals, these marks become lighter and a silvery-white color.
The Science Behind Stretch Marks
To understand how stretch marks form, it helps to know a little about how your skin is structured. Think of your skin as having layers; the outer layer you can see and touch is called the epidermis, and just beneath it is a deeper layer called the dermis. The dermis acts like a support network, filled with fibers called collagen and elastin that keep skin strong, firm, and able to bounce back when stretched.
When skin is stretched slowly with gradual weight gain or muscle building, those fibers have time to adapt. But when skin stretches faster than those fibers can keep up with, they become damaged and disorganized. This is what creates a stretch mark: essentially, a scar within the dermis where the support structure has been disrupted.
Hormones also play a bigger role than most people realize. High levels of cortisol (stress hormone) can weaken the skin’s collagen fibers even before any stretching occurs. This is why some people are more prone to stretch marks than others, even when they go through the same physical changes.
Types of Stretch Marks
There are two primary types of stretch marks. Striae rubrae are new or active marks that appear reddish, pink, or purplish because dilated blood vessels are still visible in the damaged tissue. For some, this may cause some itching or tenderness in these areas. Striae albae are older, mature marks that have faded to a white or silvery color; these are classified as atrophic, wrinkled, and hypopigmented, and have been described as appearing similar to mature, flattened dermal scars. Pregnancy-related stretch marks are sometimes referred to specifically as striae gravidarum, and marks caused by steroids that increase cortisol are also considered a sub-type of stretch mark.
Causes of Stretch Marks
One of the most common causes of stretch marks is pregnancy. Anywhere from 43-88% of pregnant women may experience stretch marks, according to the National Library of Medicine. As a baby grows in the womb, it can cause the skin on the abdomen to stretch rapidly which may lead to stretch marks appearing during pregnancy. Other causes include significant weight gain in a short period or during puberty as growth spurts can cause rapid stretching of the skin.
Can I Treat Stretch Marks?
Several treatment options exist, and effectiveness varies significantly depending on whether the stretch marks are in the active (rubrae) or mature (albae) stage — earlier intervention generally yields better results.
Topical retinoids
Retinoids such as tretinoin (Retin-A), derived from vitamin A, may improve the appearance of stretch marks less than a few months old by helping to rebuild collagen in the skin. In a double-blind, randomized controlled study, 80% of tretinoin-treated patients showed definite or marked improvement after 6 months, compared to just 8% in the control group with early-stage stretch marks. However, tretinoin is significantly less effective on older, white stretch marks, and should not be used during pregnancy or while nursing without consulting a healthcare provider.Laser therapy
Different laser types are used depending on the stage of the stretch mark. The 1064-nm long-pulsed Nd:YAG laser has demonstrated clinical improvement in erythematous (red) striae, likely due to its affinity for the vascular target oxyhemoglobin, and also induces new collagen formation. Fractional CO2 laser is typically used for texture improvement in older, white stretch marks.Microneedling
This uses small needles to stimulate collagen production in the dermis. It can be effective alone or in combination with other treatments, particularly for mature stretch marks.OTC creams
No single therapy has been advocated to completely eradicate stretch marks, and the literature provides no gold-standard therapy. Many over-the-counter products make broad claims, but the clinical evidence behind most is limited. Consulting a dermatologist is the best way to identify a treatment plan suited to your skin type and the age of your stretch marks.
How Do I Prevent Stretch Marks?
While it may not be possible to completely prevent stretch marks, certain habits may help minimize their likelihood or severity. Staying well-hydrated, maintaining a stable body weight, and exercising regularly to support skin elasticity are reasonable steps. However, it’s important to set realistic expectations: there is no evidence that creams used during pregnancy prevent stretch marks. Anyone concerned about stretch marks should speak with a board-certified dermatologist or healthcare provider, who can offer guidance tailored to their skin type, life stage, and treatment goals.