Congenital valve defects in veins, thrombophlebitis, pregnancy and old age are some conditions that cause veins to protrude, according to HealthGrades. Other possible causes include living a sedentary lifestyle and obesity. Any condition that obstructs the flow of blood in veins may cause them to protrude.
Veins are hollow, flexible tubes with one-way flaps called valves that help keep the blood flowing in one direction, explains WebMD. When the valves in veins become damaged, blood can begin to flow backwards or in both directions, causing the veins to swell. As humans age, their veins weaken and lose elasticity, which may cause the valves to malfunction and the veins to enlarge and protrude from under the skin, explains HealthGrades. Inflammation and swelling in the veins due to various medical conditions, such as diabetes, or lifestyle choices, such as lack of movement or smoking, may cause poor blood circulation, which can cause valves to malfunction and veins to swell, notes WebMD.
Veins that protrude from the skin are called varicose veins. In extreme cases, varicose veins look like twisted blue cords running right below the surface of the skin, and they can be tender to the touch. In most cases, however, these veins are not painful and are typically harmless. Bulging veins is common, and women are more likely to develop them than men, explains WebMD. However, they can also be a symptom of a serious condition, so individuals should seek medical attention if bulging veins appear, notes HealthGrades.