Stretch marks closely resemble scars. In fact, stretch marks are the most common types of skin lesions. About 90% of pregnant women get stretch marks. They also affect 70% of adolescent females and about 40% of young males. In medical terminology, stretch marks are called striae. Mature stretch marks are devoid of color, and newer stretch marks are often red or purplish in color.

Stretch marks develop when the skin is excessively stretched, damaging the collagen fibers and proteins in the underlying skin layer called the dermis. Scientists believe that shattering of collagen leads to dilation of small blood vessels (called capillaries) that results in red or purple-colored early stretch marks. Inflammation and collagen remodeling may lead to the loss of pigment-producing, melanocyte cells or obscuring of melanin pigment. Over time, this
lack of pigment results in the white or hypo pigmented scars that most people associate with mature stretch marks.Growth spurts and sudden or excessive weight
gain cause stretch marks to form in young people. Young women commonly get them on their breasts, thighs, hips and buttocks. Young men often develop stretch marks from participating in certain body-altering sports such as weightlifting or from the use of dangerous bodybuilding steroid drugs. Women commonly develop stretch marks
on their lower abdomen in the last months of pregnancy.