Genetics

Most women with spider veins have mothers and/or female relatives with this vein condition. Weak vein walls and valves, as well as shortage of vein valves, seem to be inherited characteristics, and may play a role in determining who develops spider veins and at what age.

Pregnancy

During pregnancy, and to a lesser degree also during periods, fluctuations in the female sex hormone (especially estrogen and progesterone), cause softening of the vein walls and valves. This makes women's veins more prone to stretching and enlargement with increased pressure.

Increased blood volume, which is needed to provide circulation to the fetus, also cause increased pressure on the vein walls. The growing fetus also exerts pressure on the pelvis, which in turn, exerts pressure on the leg veins.

Some women see spider veins that develop during their pregnancies and persist after their baby is born. Other see that their veins disappear after the baby is born, only to reappear later in life.

Prolonged standing and sitting

Prolonged standing and sitting cause a great amount of pressure to develop in the leg veins. In both conditions, the calf muscles are inactive and therefore cannot help push the venous blood to return to the heart. This causes blood to pool in the veins, thus resulting in increased pressure on the vein walls.

This pressure drops once one begins to walk, so if your job requires you to stand or sit for prolonged periods, remember to take short breaks and walk around for a couple of minutes every hour.

Injury

In some people, spider veins appear after injury or trauma to the vein, such as after a broken ankle, surgery, car accident, or sports injury. Bruising, which is pooled blood resulting from broken veins under the skin, can also lead to an inflammatory response, which in turn, can result in enlarged veins. Sometimes, spider veins can appear many years after the wound has healed.

Vein Conditions

In men, spider veins are usually the result of blow-outs from nearby varicose veins. High pressure from these veins cause adjoining superficial veins to stretch, enlarge, and change in color. These spider veins are usually darker and have larger diameters than the spider veins in women.

Spider vein matting, which resemble bruisings that do not go away, is often caused by the healing process of injuries and bruises, as well as complications from sclerotheraphy.

Ankle flares, or spider veins found on the inside ankle, is often associated with chronic venous insufficiency (CVI), a condition where venous blood is not returned efficiently to the heart.

Causes of Facial Spider Veins

Although for most people spider veins occurs in their legs, there are instances where fine veins in the face and nose area become enlarged and darker in color.

For some, prominent facial veins are caused by rosacea. This condition is marked by numerous red spider veins in the nose, cheeks, forehead, and chin, and is sometimes accompanied by acne breakouts. Although the cause of rosacea is unknown, it seems that alcohol and spicy food consumption, as well as stress, may play a role.

Chronic sun exposure can also cause spider veins, as well as other forms of skin damage such as wrinkles, freckles, moles, and skin cancer. Trauma, such as bruising, can also lead to spider veins.

In some people with chronic allergies and inherited predisposition to vein conditions, repetitive sneezing and coughing can lead to enlargement of veins around the nose and below the nostrils. Bouts of violent vomiting can also create enough pressure to cause spider veins to form in the cheecks.