Understanding Stretch Marks — Why They Form and What Actually Treats Them

Medically reviewed by Dr. Dan Xu, M.D., CCFP — CPSO Licensed Physician and Founder & Medical Director of ID Cosmetic Clinic, Markham. Last updated June 2026.

Stretch marks (striae distensae) are one of the most common skin concerns in the world — affecting around 80% of pregnant women, plus large numbers of people who go through rapid weight change, puberty growth spurts, or muscle gain. Despite how universal they are, they remain one of the most misunderstood concerns in skincare and aesthetic medicine. Patients arrive at our Markham clinic having spent years and money on oils and “miracle” creams, frustrated that nothing changed. The reason is simple: most stretch-mark products target the wrong layer of skin. Understanding what a stretch mark actually is — and where it lives in the skin — is the first step to choosing a treatment that can genuinely help.

What stretch marks actually are: scar tissue in the dermis

A stretch mark is not a pigment problem on the surface (the epidermis). It is a form of scarring in the dermis — the middle, structural layer of skin — that occurs when the skin is stretched faster than its collagen and elastin can adapt. Under the strain, those fibres tear, and the body repairs the gap with disorganised, thinner scar tissue.

Under the microscope, a stretch mark shares features with other scars: the normal, basket-weave structure of collagen is replaced by flattened, aligned bundles; elastic fibres are reduced or fragmented; and the dermis is measurably thinner than the surrounding skin. This is why a stretch mark often looks slightly depressed, shiny, or feels softer and thinner to the touch than normal skin.

This biology dictates everything about treatment. Because the damage is in the dermis, any treatment that works has to reach and remodel the dermis — stimulating new collagen and elastin. Creams and oils that sit on the epidermis can improve hydration and the look of texture slightly, but they cannot rebuild torn dermal architecture. That is the honest reason topical products so often disappoint.

The two stages: red stretch marks vs white stretch marks

Stretch marks evolve through two distinct stages, and knowing which stage you are in is the single most important factor in how well treatment will work.

Early stage — red/purple (striae rubra)

• Colour: pink to deep purple-red.
• Feel: slightly raised, sometimes itchy.
• What’s happening: the dermis is still inflamed, blood vessels are active, and hair follicles and oil glands are still present within the mark.
• Treatment window: this stage responds best. Inflamed skin is biologically more active and more capable of repair, so laser and microneedling can remodel collagen far more effectively here.

Mature stage — white/silver (striae alba)

• Colour: white to silvery, with a flat or slightly sunken surface.
• Feel: the skin is thinner and softer than the surrounding area.
• What’s happening: inflammation has settled, the scar tissue is stable, and the active blood supply is gone.
• Treatment window: still treatable, but it takes more sessions and the improvement is more modest.

The practical takeaway: if your stretch marks are still red or purple, do not wait. Treating them early, while they are still inflamed, gives the best possible result. If they have already turned white, treatment is still worthwhile — it simply requires patience and a more aggressive, combined approach.

Why they form: it’s not just “stretching”

Mechanical stretching is the trigger, but it does not fully explain why two people with the same pregnancy or the same weight gain can end up with completely different results. Research points to several factors working together:

• Hormones. High levels of corticosteroid hormones — during pregnancy, puberty, or with steroid use — suppress fibroblasts’ ability to make collagen, leaving skin more fragile and easier to tear. This is a major reason stretch-mark severity varies so much between individuals under the same degree of stretching.
• Genetics. Stretch marks run in families. If your mother had them, your odds are meaningfully higher — a strong hint that the underlying tendency is inherited.
• Baseline skin quality. Skin hydration and collagen density influence how much stretch the dermis can absorb before fibres break.
• Speed of stretching. Skin that is stretched slowly tolerates it far better than skin stretched quickly — which is why rapid weight or muscle gain (and the fast growth of late pregnancy) is so often the culprit.

Because so much of this is hormonal and genetic, it is worth being honest: stretch marks are extremely common and are not a sign of doing anything wrong with your body. They are a normal human response to skin under strain.

What actually treats stretch marks: the evidence-based options

No single treatment “erases” a stretch mark completely. The realistic, honest goal is meaningful improvement — making marks narrower, flatter, closer in colour to surrounding skin, and less noticeable. The treatments with the strongest clinical evidence all work by remodelling the dermis, and the best choice depends on whether your marks are red or white.

For red stretch marks (early stage)

• Pulsed-dye laser (PDL): targets the active blood vessels, reducing the red and purple colour. Most effective in the early stage while vessels are still present.
• Non-ablative fractional laser: stimulates collagen rebuilding and improves the texture of the marks with little downtime.
• Intense pulsed light (IPL): helps even out colour irregularity.

For white stretch marks (mature stage)

• Ablative fractional laser (CO₂, Er:YAG): deeper, stronger dermal stimulation — more powerful results, but a longer recovery period.
• RF (radiofrequency) microneedling: delivers radiofrequency heat into the deep dermis to drive collagen remodelling. The category includes branded devices such as Morpheus8 and Potenza; at ID Cosmetic Clinic we use comparable RF-microneedling technology (Lutronic Genius / Sylfirm X). This is often a workhorse for mature, stubborn marks, and tends to be well tolerated across a range of skin tones.
• Traditional microneedling: gentler, a good entry point for a first treatment or as maintenance between laser sessions.

Stretch mark treatment options at a glance

Two principles hold across almost every case. First, most patients need 4–8 sessions to see significant improvement — stretch marks are scars, and remodelling scar tissue takes repeated stimulation over months. Second, combined plans outperform any single device. Pairing a laser that addresses colour with RF microneedling that rebuilds depth, for example, usually beats relying on one machine alone.

A note on skin tone

Device choice matters even more for medium and deeper skin tones, which are more prone to post-inflammatory hyperpigmentation (temporary darkening) after aggressive resurfacing. Our Markham practice primarily serves Asian faces, and we choose settings and technologies — frequently RF microneedling, which heats the dermis while sparing more of the surface — specifically to lower that risk. If you have a deeper skin tone, ask any provider directly how they adjust for pigmentation safety; the answer tells you a lot about their experience.

Realistic expectations: what “improvement” honestly means

It is important to set expectations clearly, because the internet does not. No treatment makes a stretch mark vanish to invisible, perfect skin. What good treatment can do is make marks substantially less obvious — narrower, flatter, better matched in colour, and finer in texture. For many patients that change is genuinely life-changing in how they feel about their skin; but a provider who promises total erasure is not being straight with you.

Results also build slowly. Because you are stimulating new collagen, the skin keeps improving for months after a session, and the full benefit of a treatment course often is not visible until several months after the last appointment. Patience is part of the treatment. And prevention deserves a mention: keeping skin well-hydrated and managing the speed of weight or muscle change can reduce the odds of new marks forming, even though no cream can guarantee prevention.

Who should be cautious — and when to wait

Stretch-mark treatments are generally safe in trained hands, but they are not for everyone at every moment. You should postpone or avoid energy-based treatment if you are pregnant or breastfeeding (most clinics wait until well after delivery and weaning), if you have an active skin infection or open wound in the area, a history of keloid or hypertrophic scarring, an active flare of conditions like eczema or psoriasis at the site, or if you have a recent tan or are taking medication that affects light sensitivity or wound healing. Certain devices also have specific precautions for very deep skin tones. A proper medical consultation screens for all of this before any treatment begins. This article is general information, not medical advice — your own plan should come from an in-person assessment.

The real takeaway

Stretch marks are dermal scars, not surface stains — so they need treatments that reach and rebuild the dermis, not creams that sit on top of it. The best results come from acting while marks are still red, choosing the right laser or RF-microneedling combination for your stage and skin tone, and being patient through a multi-session course. Improvement is realistic; perfection is not. Choose a physician-led clinic that will tell you that honestly, tailor the technology to your skin, and prioritise pigment safety — and you give yourself the best chance of a result you are genuinely happy with.

Related at ID Cosmetic Clinic

• Treatment: RF Microneedling
• Treatment: Fractional Laser Resurfacing
• Treatment: Microneedling
• Condition: Stretch Marks (Striae)
• Compare: RF Microneedling vs Laser: Which Is Right for You?
• Read next: A Doctor’s Guide to Treating Acne Scars