The term “tiger stripes” is a widely used, informal name for stretch marks, which are medically known as striae distensae. These linear, often indented streaks are a form of dermal scarring that occurs when the skin is rapidly stretched. They are an extremely common and natural consequence of the body undergoing significant physical changes throughout life. While completely harmless from a medical standpoint, they represent a disruption in the skin’s structure that some people find cosmetically concerning.
The Biological Origin of Stretch Marks
Stretch marks are not a surface-level skin issue, but rather a structural breakdown that happens in the dermis, the layer of skin beneath the visible epidermis. The dermis houses the connective tissue fibers that provide skin with its strength and elasticity. These fibers are primarily collagen, which gives tensile strength, and elastin, which allows the skin to stretch and recoil.
When the skin is subjected to a rapid, excessive pulling force, the dermis literally tears beneath the surface. This sudden tension causes the collagen and elastin fibers to become fragmented and disorganized, exceeding the skin’s natural capacity to expand. The process of stretch mark formation also involves a complex biological response, including inflammation.
The appearance of the marks changes over time, reflecting different stages of this dermal damage. Initially, they are called striae rubrae and appear reddish, pinkish, or purplish because the underlying dilated blood vessels are visible through the thinned skin. As the inflammatory process subsides and the tissue attempts to heal, the marks mature into striae albae, which are typically white, silver, or flesh-colored. This mature stage signifies a permanent scar where the normal basket-weave pattern of collagen has been replaced by scar-like tissue and the blood vessels have regressed.
Primary Causes for Their Development
Stretch marks are caused by physical events that place extreme mechanical stress on the skin, coupled with hormonal factors that reduce the skin’s resistance. The most frequent physical triggers involve rapid changes in body size or shape, such as puberty growth spurts. These spurts cause the body to rapidly increase in height and width, often leading to marks on the thighs, breasts, and buttocks.
Pregnancy is another common trigger, specifically the rapid abdominal expansion during the later trimesters, leading to striae gravidarum in up to 90% of women. Significant weight gain or loss, as well as rapid muscle development from intense weight training, can also overstretch the skin. Marks often correspond to the area of maximum tension, such as the abdomen, hips, breasts, and shoulders.
Hormonal influences also play a significant role, particularly the hormone cortisol. Cortisol, produced by the adrenal glands, weakens elastic fibers and inhibits new collagen production. Elevated cortisol levels, such as those occurring during pregnancy or in conditions like Cushing syndrome, make the dermis vulnerable to tearing. Prolonged use of high-dose oral or topical corticosteroid medications can mimic this effect.
Options for Appearance Management
Since stretch marks are a form of scar tissue, complete removal is not possible, but their appearance can be significantly reduced. Management focuses on fading the color and improving the texture of the damaged skin. The most effective treatments are performed during the early, reddish striae rubrae phase when the marks are still active.
Topical treatments are the most accessible option, though they offer limited effectiveness, especially on mature white marks. Ingredients like retinoids, specifically tretinoin, can speed up cell turnover and stimulate collagen production, improving the appearance of newer marks. Hyaluronic acid and moisturizing agents are used to hydrate the skin, which can improve overall elasticity and texture.
Clinical procedures target deeper dermal damage to encourage the skin to regenerate collagen and elastin. Laser therapy is a common approach. Pulsed dye lasers are effective for new, red marks by targeting the blood vessels that cause discoloration. Fractional lasers, which create microscopic injuries to stimulate healing, are used for mature, white marks to improve texture and encourage collagen remodeling.
Microneedling is a minimally invasive technique that uses fine needles to create controlled micro-injuries in the dermis. This triggers the skin’s natural wound-healing cascade, resulting in increased production of collagen and elastin to smooth the scar tissue. Microdermabrasion, a gentler procedure that exfoliates the outermost layer of skin, can improve overall texture and make mild stretch marks less noticeable, but it is not effective for deeper, older marks.