Prominent veins on the hands are obvious may be physiological, blood reflux obstruction, varicose veins and other causes. 1. Physiological: Physiological causes include people who have been engaged in physical labor or exercise for a long time. Due to the fast blood flow for a long time, the blood vessels are thickened, which is manifested as prominent and obvious veins on the hands. 2. Obstruction of blood return: Narrowing or blockage of veins in the upper limbs can lead to obstruction of venous return and expansion of superficial venous tortuosity which can result in the phenomenon of prominent veins on the hands. 3. Varicose veins: usually varicose veins in the upper limbs are rare, but when the lesions in the upper limbs or armpits compress the veins, they can cause varicose veins in the upper limbs, which can lead to the phenomenon of prominent veins on the hands. There are many reasons for the prominent veins on the hands, after eliminating the physiological reasons, we should consult the doctor in time, clarify the cause of the disease under the guidance of the doctor, and take effective treatment.