These blood clots often occur because of a combination of 3 factors:

Changes in your blood chemistry

If your blood becomes more viscous (thicker), it is more likely to clot. Certain drugs, such as the contraceptive pill can make your blood more viscous.

Trauma or damage to a vein

Damage to the structure of your veins, in particular any damage to the valves in your veins (the one-way swing doors in your veins which prevent the blood flowing backwards) increases the likelihood of a clot.

Stasis

Stasis is a lack of movement. When you move around the muscles in your legs contract to help squeeze the blood in your legs back up to your heart. When you sit still for a long time, such as during long aeroplane flights, this doesn't happen and blood can pool in your legs.

Compression stockings, socks and tights can make a real difference in treating DVT.

When travelling

Scholl make Flight Socks, available from your local pharmacy, to help protect your legs when travelling. For more information about Flight Socks, visit www.Schollflightsocks.com.

Preventing post-thrombotic syndrome

If you have had a DVT in your leg, whatever the cause, you are at risk of a condition known as post-thrombotic syndrome (PTS). The symptoms include discolouration of your skin, discomfort and swelling.

Left untreated, a leg affected by PTS may develop a venous ulcer.

Wearing compression stockings, socks and tights has been shown to be a very effective way of preventing post-thrombotic syndrome.