Purple streaks on thighs may be physiologic phenomenon, phlebitis, varicose veins and so on. 1. Physiological phenomenon: purple stripes on thighs are physiological normal veins, which are common in people with thin body types. It may also be the body obesity lines, is the phenomenon caused by adolescent puberty growth. Just have purple lines, there is no other disease, no need for special treatment. 2. Phlebitis: Inflammation of the veins in the legs, patients may have purple lines on the thighs, pale skin color, numbness, coldness, redness, swelling and pain, subcutaneous nodules and other manifestations. 3. Varicose veins: In varicose veins, there are purple lines on the thighs, vein clusters, redness, swelling, pain, ulcers and so on. If you have purple veins in thighs, you should pay attention to observation, and if you can’t tell whether it is abnormal or not, it is recommended to go to the hospital in time and follow the doctor’s instructions for symptomatic treatment.