Stretch marks, known medically as striae distensae, are a common skin concern that can appear on various parts of the body. They are a type of scarring that affects many individuals. These marks signify changes within the skin’s structure.
How Stretch Marks Form
Stretch marks develop when the skin undergoes rapid stretching or shrinking, damaging its underlying layers. The dermis, the middle layer of the skin, contains essential fibers like collagen and elastin that provide strength and elasticity. When the skin stretches too quickly for these fibers to accommodate, they can rupture or tear. This mechanical stress is a primary factor in their formation.
Common scenarios include significant growth spurts during puberty, rapid weight gain or loss, and pregnancy. Rapid muscle growth from weight training can also contribute to their appearance.
The Science Behind Red Stretch Marks
New stretch marks appear red, pink, reddish-brown, or purple, depending on skin tone. This initial coloration results from the body’s inflammatory response to dermal tearing. When collagen and elastin fibers in the dermis rupture, the body initiates a healing process. This involves increased blood flow to the damaged area and the formation of new blood vessels, a process called angiogenesis.
The increased visibility of these blood vessels through the thinned epidermis contributes to the reddish or purplish hue of new stretch marks, which are medically termed striae rubrae. This phase indicates active healing and inflammation. The body repairs the damaged skin, leading to the characteristic red appearance.
Why Stretch Marks Change Color
Over time, red stretch marks undergo a color change, fading to lighter hues such as white or silvery streaks. This change signifies the progression from the initial inflammatory phase to a more mature, scarred stage. As healing continues, inflammation subsides, and newly formed blood vessels that contributed to the redness begin to contract and diminish.
The body replaces the damaged collagen and elastin with a different type of scar tissue. This mature scar tissue, known as striae albae, lacks the pigment and vascularity of normal skin, appearing lighter, often shiny, and sometimes slightly depressed. While the color fades, the underlying structural changes in the dermis mean that stretch marks are a permanent form of scarring, though their appearance can become less noticeable over time.