Stretch marks, medically known as striae distensae, are a type of scar that forms when the underlying skin tissue is rapidly stretched beyond its natural capacity. This rapid expansion typically occurs during periods of quick change, such as rapid weight gain, growth, or pregnancy. Although these marks may become more noticeable after significant weight loss due to the skin contracting, the damage that created the stretch mark happened during the preceding rapid change, not the loss itself.
The Actual Science of Stretch Marks
The skin is composed of three main layers, and the middle layer, the dermis, is where stretch marks originate. This layer contains the connective tissue fibers, collagen and elastin, which provide the skin with its strength, structure, and ability to stretch and snap back. When the skin expands too quickly, these fibers are overextended and tear, much like a rubber band stretched past its breaking point. The body attempts to repair this damage, but the resulting formation is scar tissue, which is visibly different from the surrounding dermal tissue.
Hormones also influence the skin’s susceptibility to tears during rapid change. Elevated levels of cortisol, produced by the adrenal glands, can weaken the elastic fibers in the skin. This reduction in elasticity makes the dermis more prone to tearing when mechanical stress is applied from within. The combination of physical tension and hormonal influence creates the conditions necessary for stretch marks to form.
Common Triggers for Skin Stretching
The most recognized trigger for striae is pregnancy, where the abdomen and breasts expand significantly over a short period. Beyond this, any period of rapid increase in body volume can cause the skin to tear. This includes weight gain, whether due to a change in diet or a medical condition that causes fluid retention.
Adolescence is another common time for their development, as rapid growth spurts can occur where the body increases in height and mass faster than the skin can adjust. Men who engage in intensive resistance training or bodybuilding often develop stretch marks on the shoulders, arms, and thighs as muscle mass increases quickly. Certain medical conditions, such as Cushing’s syndrome, which causes prolonged exposure to high cortisol levels, can also trigger the formation of wide, distinct stretch marks.
Appearance and Evolution of Stretch Marks
Stretch marks are initially classified as striae rubrae, meaning red streaks, because they appear reddish, pink, purple, or dark brown, depending on the individual’s skin tone. At this early stage, the marks are slightly raised or inflamed due to the inflammatory response to the dermal tearing. The color is vivid because the underlying blood vessels are still visible beneath the newly damaged skin.
Over time, these marks mature and transition into striae albae, or white streaks. The inflammation subsides, the blood vessels contract, and the scar tissue loses its initial coloration. This results in the marks becoming pale, white, or silvery, and they often become slightly sunken or indented with a finely wrinkled texture. Once they reach this mature stage, they are permanent scars that are more resistant to topical treatments.
Strategies for Minimizing Their Appearance
Addressing stretch marks when they are in the early, colored stage is generally more effective than waiting until they mature into white scars. The goal of most interventions is to stimulate the production of new collagen and elastin fibers to remodel the damaged dermal tissue.
Topical Treatments
The most scientifically supported topical agents are retinoids, specifically prescription-strength tretinoin, which is a derivative of Vitamin A. Tretinoin works by accelerating cell turnover and stimulating collagen synthesis in the dermis, which can improve the appearance of newer, red stretch marks. However, retinoids are not recommended for use during pregnancy or breastfeeding. Hyaluronic acid, a substance naturally found in the skin, can also be applied topically to hydrate the skin and may help improve the appearance of new striae.
Clinical Procedures
For more mature, white stretch marks, a variety of clinical procedures can be used to induce dermal remodeling. Laser therapy, such as pulsed dye laser, is often effective on red stretch marks by targeting the blood vessels to reduce redness. Fractional laser treatments create micro-injuries in the skin to stimulate new collagen and are often used for the texture improvement of white scars. Microneedling is a procedure that uses fine needles to puncture the skin, triggering the body’s natural wound-healing response and increasing collagen and elastin production to improve skin texture.