Varicose eczema is usually caused by varicose veins, which develop when the small valves inside the veins stop working properly.
Varicose veins are swollen and enlarged veins that are usually blue or dark purple. They may also be lumpy, bulging or twisted in appearance.
Inside your veins there are one-way valves that open to let the blood through and then close to prevent it flowing backwards.
Sometimes, the walls of the veins can become stretched and lose their elasticity, causing the valves to become weakened. If the valves do not function properly, the blood may leak backwards past the valves. If this happens, the blood collects in your veins, which become swollen and enlarged (varicose veins).
This causes the pressure inside these veins to increase, which can damage the skin and lead to varicose eczema, as well as more severe skin damage such as lipodermatosclerosis or a venous leg ulcer.
It is not fully understood why the walls of the veins stretch and the valves weaken. Some people develop the condition for no obvious or apparent reason, although there are some risk factors, such as age or being pregnant (see below).
Read more information about the causes of varicose veins.
Deep vein thrombosis
Deep vein thrombosis (DVT) is a blood clot in one of the deep veins in the body. A blood clot in one of the veins in your leg may block the flow of blood and damage the valves. This can increase pressure in the vein and lead to severe skin damage, such as lipodermatosclerosis.
DVT sometimes occurs for no apparent reason, but may be more likely to occur if you are immobile (unable to move) for a long period of time - for example, if you are recovering from an operation in hospital. There are a number of other possible causes and risk factors, such as heart and lung disease.
Read more information about the causes of DVT.
A number of things can increase your likelihood of developing varicose eczema and lipodermatosclerosis, including:
age - as you get older, your veins start to lose their elasticity and the valves inside them stop working as well
gender - varicose eczema is more common among women
weight - being severely overweight puts extra pressure on your veins, which means that they have to work harder, and also increases the pressure on the valves, making them more prone to leaking
You can use the healthy weight calculator to find out whether you are overweight.