Stretch marks, or striae, occur when the skin is stretched rapidly due to factors like pregnancy, puberty, rapid weight gain, or certain medical conditions. The skin’s collagen and elastin fibers tear under pressure, leading to visible, often red or purple marks that fade to a lighter color over time. Hormonal changes, particularly involving corticosteroids, can also weaken the skin’s elasticity. Treatments for stretch marks include topical creams with retinoids or hyaluronic acid, which can improve skin texture.

Scarring occurs when the skin heals after an injury, acne, surgery, or burns, leading to the formation of fibrous tissue. Factors like genetics, the severity of the injury, and inflammation during healing influence the extent of scarring. Deeper wounds tend to cause more pronounced scars. Acne scars, for example, result from inflammation that damages skin tissue. Treatments for scarring include topical creams with ingredients like silicone or retinoids, which promote skin healing and reduce scar appearance.