Weak vein walls and valves are typically the cause of varicose veins.
There are microscopic one-way valves inside your veins that open to let blood through and seal to stop it from going backwards.
Sometimes the veins’ walls stretch and lose their elasticity, weakening the valves in the process.
The blood may leak and flow backward if the valves are not working properly. If this occurs, the blood builds up in your veins, causing them to swell and expand.
Uncertainty surrounds the causes of venous valve deterioration and stretching of the vein walls. Some people get the illness for no visible or evident reason.