Purple streaks at the base of the thighs are considered a high probability of swelling streaks, which are caused by the breakage of the elastic fibers of the skin, resulting in skin lesions. Common causes include sudden weight gain, excessive growth, or long-term high oral doses of topical glucocorticoids. They usually appear as purple streaks with bulges in the early stages and turn silvery white with slightly depressed streaks in the later stages. Swellings affect the aesthetics, but have no effect on health, and there is no specific treatment for them. For the early appearance of swollen lines, topical application of topical vitamin A cream or cosmetic laser can be used to relieve them; for the old swollen lines, there is no effective treatment, and it is recommended to actively control weight and avoid high doses of long-term application of glucocorticoids.