The reason why the blood vessels on the legs are blue may be that some people have white skin and less subcutaneous fat because of genetic reasons, and the blood vessels on the legs may appear physiologically blue, which is a normal phenomenon and does not need to be treated. It may also be caused by congenital weakness of the vein wall, varicose veins, phlebitis and deep vein thrombosis of the lower limbs, etc. 1. congenital weakness of the vein wall: some people have congenital weakness of the vein wall, which leads to poor venous reflux, so that some of the venous blood stagnates in the blood vessels, resulting in the obvious phenomenon of blue blood vessels on the legs; 2. varicose veins: if the venous blood reflux continues to be poor, the blood that stagnates in the blood vessels increases The pressure on the venous cavity will increase, the blood vessels will dilate, the venous valves will not close completely, and varicose veins will appear. Patients will have discomfort in both lower extremities, which is aggravated by standing, and can see the greenish veins raised in the shape of earthworms, and some serious patients will have ulcers, bleeding and phlebitis. For mild varicose veins, no special treatment is usually needed and elastic stockings can be worn under the guidance of a doctor. For aesthetic purposes, sclerotherapy can also be used to depress the veins by injecting sclerosing agents, or laser treatment can be taken. If the varicose veins are more serious, you need to go to the hospital as soon as possible according to the situation and undergo the corresponding surgical treatment; 3. Phlebitis: It is often caused by the stimulation of the legs by cold and moisture factors, etc. In addition to the very obvious bruising of the blood vessels on the legs, it is usually accompanied by itching, pain and reduced local skin temperature. If combined with bacterial infection, it can be treated with drugs under the guidance of doctors, and can also be coated with topical anti-inflammatory ointment, and can be treated with surgical excision if necessary. 4. Lower limb deep vein thrombosis: It is common in post-operative patients and patients in coma with impaired consciousness, mainly due to the lack of movement of the lower limbs, resulting in obstruction of deep vein blood return and the formation of blood in a hypercoagulable state. The clinical symptoms are swelling, pain and obvious bruising of blood vessels in the affected limbs. Patients can rest in bed and elevate the affected limb to promote the swelling to subside. Anticoagulant drugs can be applied to inhibit the development of thrombosis, analgesics can be applied to relieve the symptoms of pain, and thrombolytic drugs can be applied for thrombolytic treatment as prescribed by the doctor.