What causes stretch marks?

Why do stretch marks appear?

The change happens in the dermis, the layer beneath the skin's surface. Collagen gives skin structure and strength, while elastin lets it stretch. When those supporting fibres break during a rapid change in size, healing leaves the narrow lines called stretch marks, or striae. Stretch marks are scars beneath the surface, so an erasing cream has given itself a rather ambitious job description.24

Not everyone develops stretch marks during the same physical changes. Having a family member with stretch marks raises your likelihood of getting them, and changing hormone levels seem to play a role. Stretch marks are common and harmless, although their appearance can bother you.13

Common sites include the abdomen, breasts, hips, thighs, buttocks, upper arms and lower back. The location often reflects where growth or a change in size has happened: an enlarging abdomen during pregnancy, developing breasts during puberty, or muscles growing quickly through bodybuilding.25

Can stretch marks appear without weight gain?

Yes. Rapid weight loss, growth spurts and rapid muscle growth can all cause stretch marks. Long term steroid use and certain medical conditions are other possibilities. Weight gain is one trigger, not a requirement, so the presence of stretch marks alone does not tell you what caused them. If no physical change or other clear cause explains new marks, arrange a medical appointment.235

Can stretch marks happen during puberty?

Yes. Rapid growth during puberty can produce stretch marks, even without pregnancy or bodybuilding. Breast development is a common example: skin stretches quickly as the breasts grow, and puberty is the most common reason for breast stretch marks. Not everyone develops them during breast growth. Marks that appear during these changes often become less noticeable with time.45

Why are stretch marks common in pregnancy?

Pregnancy combines stretching skin with hormonal changes that make stretch marks more likely. Around 8 out of 10 pregnant women develop them. Marks usually appear on the abdomen as the bump grows, and sometimes on the upper thighs or breasts. There is no single point in pregnancy when they must appear. Itchiness around thinning skin can be the first sign.6

Greater than average pregnancy weight gain increases the likelihood of stretch marks, but do not try to prevent them by eating less to lose weight while pregnant. Discuss concerns about pregnancy weight with your midwife or doctor. After birth, the marks can gradually become paler and less noticeable, though they probably will not disappear completely.6

Why do stretch marks change color?

Their color changes as the scars mature. New marks can be pink, red, purple, reddish brown or dark brown, depending on skin color, and can feel slightly raised or itchy. Older marks become lighter and often slightly sunken. Breast stretch marks can also become smaller and more wrinkled. A pale mark is usually an older scar, not evidence that the original cause is still active.14

Stretch marks generally take six to twelve months to fade. They can become less noticeable without treatment, but fading is not the same as complete removal. Older, deeper marks are harder to treat than new ones.2

Can medicines or medical conditions cause them?

Long term use of corticosteroid creams can cause stretch marks. Steroid tablets are another risk factor, including long term prednisone use. Medicines that interfere with collagen formation can also contribute. When discussing unexplained marks with a clinician, include medicines you take and any cortisone creams you have used.125

Less commonly, stretch marks are linked to conditions such as Cushing's syndrome, which involves too much of the hormone cortisol. Disorders affecting connective tissue can also be associated with them, including Marfan syndrome and Ehlers Danlos syndrome. These are possible causes to investigate when appropriate, not diagnoses you can make from stretch marks alone.25

When should you see a doctor?

Get new stretch marks checked if they appear without a clear cause. Also see a doctor if large stretch marks occur alongside more fat on the chest and abdomen but slim arms and legs, a buildup of fat around the neck and shoulders, or a red, puffy, rounded face. These can be signs of Cushing's syndrome.35

A clinician will examine the marks and ask when they appeared, whether you have had them before, what medicines you use and whether you have other symptoms. Tests are sometimes needed when ordinary physical changes do not explain them.5

Not every line on the skin is a stretch mark. An uncommon lookalike called linear focal elastosis produces yellow, palpable lines, often across the lower back. Its cause is uncertain. A clinician can distinguish it by appearance and sometimes a skin biopsy, rather than assuming every stripe needs stretch mark treatment.7

Can you prevent stretch marks?

Prevention is not always possible. Maintaining a healthy weight and avoiding rapid weight changes can reduce the chance of marks linked to those changes, but pregnancy, puberty and inherited susceptibility are not controlled by a skincare routine. Creams and lotions make plenty of prevention claims, but a jar cannot negotiate with puberty.3

Evidence for preventive creams and oils is limited. Almond oil, cocoa butter, olive oil and vitamin E have not prevented stretch marks in studies. Products containing centella or hyaluronic acid might help prevent them, but there is no dependable cream that stops everyone getting stretch marks.16

What helps once stretch marks appear?

Treatment is optional. Hyaluronic acid and prescription tretinoin can make early stretch marks less noticeable. If you try a topical product, apply it daily and massage it in gently; visible improvement takes weeks. Follow prescribed directions for tretinoin rather than treating it as an ordinary moisturiser. During pregnancy, do not use retinoid creams. If pregnant or breastfeeding, check with your doctor before starting treatment.1234

A dermatologist can discuss laser treatments or microneedling to improve appearance. Microneedling uses tiny needles to stimulate new collagen and elastin, and usually requires several sessions. Procedures can cause irritation, swelling and changes in skin color. Laser treatment needs particular care on darker skin because burns and discoloration are possible. Ask about likely improvement, side effects and cost before choosing treatment, especially for older marks.24