Thread veins, also known as spider veins or telangiectasia, are tiny blood vessels that become visible just beneath the surface of the skin. They often appear as fine red, blue, or purple lines and are especially common on the legs. Although they are usually harmless, many people notice them as they become more prominent with age or after hormonal changes, and they can be a source of cosmetic concern.
This article explains what leads to thread veins on the legs and what you can do if they are affecting your confidence or comfort.
How healthy leg veins normally work
Healthy leg veins play an important role in moving blood back towards the heart. Unlike arteries, which carry blood away from the heart under high pressure, veins rely on a combination of muscle movement and one-way valves to keep blood flowing in the right direction.
When you walk, your calf muscles act like a natural pump. Each step squeezes the deep veins in the legs and pushes blood upwards. Between each squeeze, the veins relax and refill, ready for the next movement.
Inside the veins are tiny valves that open to allow blood to travel upwards, and then close again, to prevent it from slipping back down under the force of gravity. These valves are essential for maintaining smooth circulation, especially in the legs, where the blood has the furthest distance to travel.
If the valves weaken or the vein walls lose their elasticity, blood can pool in the lower legs. This increased pressure can affect the smaller veins nearer the surface of the skin, which may become enlarged and visible as thread veins.
The main causes of thread veins on the legs
Thread veins on the legs develop for a variety of reasons. In many people, more than one factor is involved.
The main causes include:
- Genetic predisposition – A strong family history of thread veins or varicose veins increases the likelihood of developing them.
- Hormonal changes – Pregnancy, the use of the contraceptive pill, hormone replacement therapy, and menopause can all influence vein tone and make thread veins more likely.
- Ageing – As we get older, vein walls and valves naturally lose some of their elasticity. This can make surface veins more prone to widening and becoming visible.
- Venous insufficiency – When the valves in the leg veins do not work as efficiently as they should, blood can pool in the lower legs. This raised pressure often contributes to the formation of thread veins.
- Lifestyle factors – Long periods of standing or sitting, limited movement, being overweight, and smoking can all increase strain on the veins.
- Sun exposure – UV light weakens the tiny blood vessels near the surface of the skin, making them more likely to dilate.
- Trauma or pressure – A blow to the leg, previous surgery, or repeated pressure from tight clothing or certain sports can trigger localised thread veins in that area.
Although thread veins are extremely common, understanding these causes can help people make sense of why they have appeared and whether further assessment might be useful.
Considering treatment for your thread veins?
At Southwest Veins, we provide specialist care for people who want to reduce or remove thread veins on their legs. We treat thread veins of all sizes, from a few fine surface vessels to larger or more complex clusters. Our preferred approach is microsclerotherapy, which is widely recognised as the gold standard treatment for leg thread veins because it is safe, precise and highly effective.
Microsclerotherapy involves injecting a carefully selected sclerosant solution into the affected veins using an ultra-fine needle. This encourages the veins to collapse and fade gradually over the following weeks. Most people require a short course of treatment sessions, and we tailor the plan to suit the pattern and severity of each person’s thread veins.
Arrange a free initial video consultation with us by visiting our contact page.
Jamie Barwell is a Consultant Vascular Surgeon who has treated over 1000 patients with varicose vein problems, using open surgical techniques and, since 2007, foam sclerotherapy. He is a graduate of Guy’s Hospital Medical School and a fellow of Royal College of Surgeons of England.