The occurrences of grooved lines on the skin caused by prolonged stretching of the skin are the first signs of stretch marks. They first appear as reddish or purple lines, but tend to gradually fade to a lighter color. Stretch marks change in appearance with time. 

At first, they are faint pink, appearing in a line, or they are parallel band-like marks, which might be slightly itchy. They gradually enlarge and become red to purple, often with a wrinkled surface. Finally, they become white, slightly flatter and often depressed, with a crepe paper appearance of linear marks 1-10 mm wide and many centimeters long.

Stretch marks can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored. Most common places are the abdomen, under belly, breasts, upper arms, underarms, thighs, hips and buttocks. They pose no health risk in and of themselves.

The glococorticoid hormones responsible for the development of stretch marks affect the epidermis by preventing the fibroblasts from forming collagen and elastin fibers, necessary to keep rapidly growing skin taut. This creates a lack of supportive material, as the skin is stretched and leads to dermal and epidermal tearing. The affected areas appear empty and soft to the touch.