Stretch marks appear as linear streaks on the skin that has been overstretched, and they run perpendicular to maximum lines of tension in the skin. They begin as flat red lines, and over time they appear as slightly depressed white streaks. They tend to occur near the armpits, on the thighs, abdomen, chest, and groin. Their appearance is similar to changes seen on the surface of rubber balloons that have been overinflated.

There is some controversy over the precise mechanism by which striae occur. There seems to be damage to the elastic fibers of the dermis (the deeper layer of the skin) accompanied by inflammation which eventually results in scar-like changes. These changes appear to be induced by excessive physical stretching of the skin. There are some clinical situations which will predispose the skin to the formation of striae. These include the rapid and excessive increase in body mass, the excessive use of topical or systemic glucocorticoid drugs (steroids), Cushing's disease (overproduction of glucocorticoids by the adrenal gland), puberty, Marfan's syndrome and Ehlers-Danlos syndrome (two rare genetic diseases), excessively large breast implants, and pregnancy.

Excessive rapid weight gain and pregnancy are the two most common risk factors. Other risk factors include the conditions described above that predispose the skin to develop stretch marks.

Striae are rarely painful or itchy. They do not produce troublesome symptoms. They begin as long red streaks and eventually mature into long white lines.

There are a wide variety of treatments, but none of them seem to be particularly valuable in preventing or treating this condition. It is agreed that there is no real medical evidence that any creams or ointments will produce any sustained improvement in the appearance of stretch marks. The use of physical modalities such as lasers and ultrasound holds some promise, but time will tell if these treatments are effective.

Treatment and prevention

Creams, gels, lotions, laser and cosmetic surgery, have all been proposed as treatments for stretch marks, although there is little medical evidence to support the efficacy of such therapies. Current treatments are especially limited in their ability to deliver long-lasting improvements for all skin types.

Often stretch marks fade over time and become unnoticeable. For people who developed stretch marks during pregnancy, these are usually less noticeable 6-12 months after giving birth. Cosmetic camouflage (makeup) can be used to conceal marks temporarily.

Advances in laser technologies and ongoing research mean that the future looks bright for developing effective treatments for stretch marks.