What are stretch marks?
The medical name for stretch marks is ‘striae distensae’ (also referred to as stria or stria atrophican – ‘skin thinning’), which effectively means ‘a line, streak, stripe or ridge’ which develops on the skin in contrast to the surrounding skin tissues.
Stria (one) or striae (multiple) may be slightly raised or indented and display different colours and textures to the surrounding skin tissues. Areas of the body most prone to stretch marks include the breasts, abdomen, axillae (armpits) or upper arms, lower back and flank (sides of the body), hips, groin, buttocks and thighs.
Stretch marks form due to significant stretching of the dermis (the middle skin layer located beneath the epidermis or outer layer of skin), which contains nerve endings, blood capillaries, sweat glands and hair follicles. The effect of continuous and progressive tearing of the connective tissues within the dermis creates a form of dermal scarring (which presents as linear markings), mostly due to underlying rapid growth factors.
Stretch marks are thus most associated with high risk individuals going through an often transient, rapid growth phase, such as adolescents (as a result of growth spurts during puberty), women during their second and third trimester of pregnancy or bodybuilders (especially when building muscle around the shoulder areas). Stretch marks are also common among individuals who rapidly gain an excessive amount of weight, developing a large abdominal circumference, due to an unhealthy diet and lifestyle. As much as rapid weight gain is a factor in stretch mark development, so too is rapid weight loss.
Stretch marks are also associated with the prolonged use of endogenous or exogenous corticosteroids (medications used in oral form or applied to the surface of the skin), as well as medical conditions whereby the skin is exposed to excess cortisol, a steroid hormone. Such medical conditions include adrenal gland diseases like Cushing’s syndrome. Those with stretch marks associated with such medical conditions generally display more prominent and widely distributed stretch marks.
These are most typical in areas of skin that are prone to constant contact or friction (i.e. rubbing together), like the armpits, between the digits of fingers and toes or other areas of the body with skin folds.
Stretch marks can be pink / red in colour (erythematous), violet (violaceous) / dark blue (caerulea), or hypopigmented (colourless or silvery due to the depletion of melanin or melanocytes which are responsible for the body’s pigment, thus resulting in skin colour loss). Multiple markings commonly occur in a symmetrical distribution perpendicular (sometimes parallel) to the direction of skin tension lines.
Newly formed stretch marks are thin and appear pink/red in colour or may even be glossy. Over time, stretch marks take on a more scar-like appearance (with a white or even slightly silvery hue) and form textured indents with a noticeable contrast to the surrounding skin tissues.
Accidental injury to the skin can cause the tearing or ulceration of stretch mark formations.