Sclerotherapy is the most widely used procedure for treating spider veins, particularly on the legs. It involves injecting an irritating solution directly into the vein, which damages the vessel wall, triggers inflammation, and causes the vein to collapse and eventually be reabsorbed by the body. For smaller veins or those on the face, laser therapy is the preferred alternative. The right choice depends on the size of your veins, their location, and your skin type.
How Sclerotherapy Works
During sclerotherapy, a doctor uses a fine needle to inject a chemical solution, called a sclerosant, into the spider vein. This solution damages the inner lining of the vessel, causing the walls to stick together and the vein to seal shut. Over weeks, the closed vein is absorbed by surrounding tissue and fades from view.
The most commonly used sclerosants in the United States are hypertonic saline (a concentrated salt solution), polidocanol, and sodium tetradecyl sulfate. The detergent-based agents like polidocanol work by disrupting cell membranes, causing damage within minutes of injection. These agents can also be mixed with a small amount of gas to create a foam, which pushes blood out of the vein and presses the vessel walls together, making it more likely the vein stays permanently closed.
Most people need two to four sclerotherapy sessions, spaced several weeks to a month apart, to reach near-complete results. After a full treatment course, patients typically see over 80% elimination of the targeted veins. Each session takes roughly 15 to 30 minutes, and you can usually return to normal activities the same day, though compression stockings are standard aftercare.
When Laser Treatment Is a Better Fit
Laser therapy uses focused light energy to heat and destroy spider veins without needles or injections. It’s the go-to option for very small veins (under about 0.75 mm in diameter) and for spider veins on the face, where sclerotherapy is generally not recommended. The laser light passes through the skin and is absorbed by the blood in the vein, generating enough heat to collapse the vessel.
Different laser types are suited to different situations. Pulsed dye lasers have long been used for facial blood vessels and port-wine stains but are less effective on leg veins. Longer-pulse lasers, such as the Nd:YAG laser, perform better on lower-extremity spider veins. In clinical testing, a 532 nm frequency-doubled Nd:YAG laser cleared over 75% of leg spider veins after just two treatments, though it worked best on patients with lighter skin tones (Fitzpatrick skin types I through III). Darker skin absorbs more laser energy at the surface, which increases the risk of burns or discoloration.
Thermocoagulation for the Smallest Veins
Some spider veins are too tiny to inject with sclerotherapy and too small to respond well to standard lasers. For these, a newer technique called thermocoagulation uses a hair-thin needle (0.075 mm in diameter) inserted just beneath the skin’s surface to deliver a brief pulse of high-frequency energy. This heats and seals veins up to about 0.3 mm across. Devices designed for this approach, like the VeinGogh system, can safely treat any skin type, including tanned skin, which gives them an advantage over most lasers.
Choosing the Right Procedure by Location
The location of your spider veins plays a major role in which treatment your provider will recommend. Sclerotherapy is the standard for medium-sized spider veins on the legs because the injection technique works well on vessels in that range and produces reliable, lasting results. Laser treatment is typically better for facial veins, where the skin is thinner and injections carry more risk of visible complications. For extremely fine red veins on the legs that resist both sclerotherapy and laser, thermocoagulation fills the gap.
Many people have spider veins of varying sizes, and a combination approach is common. Your provider might use sclerotherapy on the larger clusters and follow up with laser or thermocoagulation on the finer ones that remain.
Why an Ultrasound May Come First
Spider veins on the legs can sometimes signal a deeper problem called venous reflux, where valves in the larger veins beneath the surface aren’t closing properly. Clinical guidelines recommend duplex ultrasound before treatment to confirm the diagnosis, check for reflux in the deeper veins, and map out the full picture of blood flow in the leg. Treating surface veins without addressing underlying reflux often leads to recurrence, so this assessment helps ensure the treatment plan targets the actual source of the problem.
Side Effects to Expect
Sclerotherapy is safe and well-tolerated, but it does carry some predictable side effects. The most common is hyperpigmentation, a brownish discoloration along the treated vein caused by iron deposits from broken-down blood cells. This occurs in up to 30% of sclerotherapy patients, with the risk varying based on the technique, the type of sclerosant used, skin tone, and post-treatment sun protection. The discoloration usually fades over several months, though in some cases it can linger for a year or more.
Another possibility is telangiectatic matting, where clusters of very fine new red veins appear near the treatment site. This tends to resolve on its own over time but can sometimes require additional treatment with laser or thermocoagulation. Bruising, mild swelling, and temporary tenderness at injection sites are also normal and typically clear within a week or two.
Laser treatments can cause redness, mild blistering, and temporary skin color changes, especially in people with darker skin. Thermocoagulation carries the lowest side-effect profile of the three options, though minor redness and pinpoint scabbing at treatment sites are common for a few days afterward.