Red blood streaks on the root of thighs are usually caused by atrophic striae, traumatic causes, localized lymphadenitis, and so on. 1. Atrophic striae: light red striae-like lesions mainly caused by the patient’s rapid weight or height growth, low birth age, long-term use of corticosteroid hormone drugs and so on. 2. Traumatic factors: patients are scraped by hard objects leading to subcutaneous damage, causing blood vessel rupture leading to bleeding, which can make the thigh root appear red blood stripes. 3. Local lymphangitis: mainly due to the lymphatic vessels are infected by hemolytic streptococcus, staphylococcus aureus and other pathogens, bacteria along the foot lymphatic vessels into the thigh root lymphatic vessels, caused by the thigh root red blood stripes. There may be other reasons for the red blood streaks at the base of the thighs, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or treatment under the guidance of the doctor.