What Causes Varicose Veins?

Varicose veins are swollen, twisted veins that sit just beneath the surface of the skin, most commonly in the legs. They affect a significant proportion of the adult population and can range from a cosmetic concern to a source of real discomfort.

How veins normally work

Veins carry blood back to the heart. In the legs, this means working against gravity. To prevent blood from flowing backwards, veins contain small one-way valves that open to let blood through and then close behind it.

What goes wrong

Varicose veins develop when these valves become weak or damaged. When a valve fails to close properly, blood leaks backwards and pools in the vein — a process called venous reflux. Over time, this increased pressure causes the vein to stretch, swell, and become visibly twisted beneath the skin.

Common risk factors

• Family history — If your parents or siblings have varicose veins, you are more likely to develop them.
• Pregnancy — Hormonal changes and increased blood volume place additional pressure on leg veins.
• Age — Vein walls and valves naturally weaken over time.
• Prolonged standing or sitting — Jobs that involve long periods on your feet reduce the efficiency of blood flow back to the heart.
• Excess weight — Additional body weight increases pressure on the veins in the legs.
• Previous DVT — A deep vein thrombosis can damage valves and increase the risk of varicose veins developing later.

Are varicose veins the same as spider veins?

Not quite. Spider veins (thread veins) are smaller, closer to the skin surface, and usually red or purple. Varicose veins are larger, raised, and often blue or green. Both can be caused by valve problems, but varicose veins are more likely to cause symptoms such as aching, swelling, and skin changes.

When to seek advice

If your veins are causing persistent aching, heaviness, swelling, or skin changes such as discolouration or itching, it is worth having a specialist assessment. A duplex ultrasound scan can identify exactly which veins are affected and whether treatment would be beneficial.