Sclerotherapy, a non-surgical treatment that involves injecting medication into blood vessels or lymph vessels that causes them to shrink.

Sclerotherapy uses a solution called a sclerosant, which is injected directly into a vein or lymph vessel. The solution irritates the vessel, causing it to swell. This swelling cuts off the flow of blood or lymphatic fluid and the vessel shrinks.

Various forms of sclerotherapy have been around since the 19th century, but techniques have improved in recent decades.

It is commonly used to treat varicose veins or so-called spider veins. It can also be used to treat blood and lymph vessel disorders that cause these vessels to form incorrectly.