The appearance of small arm veins may be physiological reasons, such as body type is thin, etc.; or pathological reasons such as: arm vein thrombosis leading to varicose and other reasons related. 1. Physiological reasons: if the body type is thin, subcutaneous fat is less, the skin color is fairer, which can make the venous vessels more obvious; people who often carry out upper limb large exercise training, such as bodybuilders, weightlifters, heavy manual laborers, will also appear such veins. 2. Pathological reasons: when patients have upper extremity venous thrombosis, venous compression, due to venous blood return obstacles, stagnation in the small arms, may appear obvious veins. It is recommended that people who have bruises on their arms should go to the hospital in time after eliminating the physiological causes, so as to clarify the causes of the disease and carry out standardized treatment under the guidance of doctors, so as not to bring adverse effects to the body due to the delayed condition.