Chronic Venous Insufficiency, or CVI, is also known as post-thrombotic syndrome or phlebitis. This condition is characterized by non-functioning valves in your veins (commonly in the legs and sometimes arms), which causes blood to pool in the limbs and an increase in internal pressure within the veins.

CVI is actually a very common affliction, affecting up to as many as 40 percent of people in the U.S. It’s more common for women, particularly after multiple pregnancies, and in middle-aged and older adults. Varicose veins and blood clots (deep vein thrombosis) are risk factors for developing CVI.

Conventional medical treatment of chronic venous insufficiency typically consists of compression treatment, which many patients don’t like due to the discomfort involved.

Two Cochrane reviews have been conducted to examine the effectiveness of horse chestnut on CVI and found that a significant number of randomized controlled trials (RCTs, heralded as the “gold standard” of scientific research) have suggested horse chestnut extract to be effective and safe for short-term treatment of CVI, while the reviewers caution that larger and more definitive trials must be conducted.

Some sources have also found that using butcher’s broom alongside horse chestnut extract in a cream is a useful treatment for varicose veins, the precursor to CVI.