Sclerotherapy closes unwanted veins by injecting a chemical solution directly into them, damaging the vein lining so the walls stick together and the vessel eventually gets absorbed by your body. It’s the most common treatment for spider veins and small varicose veins, with clinical success rates of 80 to 90% for treated vessels.
What Happens Inside the Vein
The injected solution, called a sclerosant, is essentially a medical-grade detergent. When it contacts the inner lining of a vein, it strips away the protective layer of cells that normally keeps blood flowing smoothly. This controlled chemical injury causes the vein walls to swell, become sticky, and seal shut.
Once sealed, blood can no longer flow through the vein. The body treats it like any other damaged tissue: inflammatory cells move in, scar tissue forms, and over weeks to months the vein shrinks and gets reabsorbed. Blood that used to travel through that vein simply reroutes through healthier vessels nearby. The treated vein fades from view as it breaks down, eventually becoming invisible or nearly so.
Types of Sclerosant Solutions
Two FDA-approved sclerosants are used most often in the United States. Polidocanol is a non-ionic detergent typically injected as a 0.5% or 1.0% solution in very small volumes, around 0.1 to 0.3 milliliters per injection site. Sodium tetradecyl sulfate is available in 1% and 3% concentrations, with each injection delivering 0.5 to 2 milliliters and total treatment capped at 10 milliliters per session.
Lower concentrations treat smaller spider veins. Higher concentrations tackle larger reticular veins and small varicose veins. Your provider selects the concentration and volume based on the size and type of veins being treated.
Liquid vs. Foam
The same sclerosant solutions can be mixed with a small amount of air or gas to create microfoam. Foam displaces blood inside the vein more effectively than liquid, which means it stays in contact with the vein wall longer and works especially well on slightly larger veins. Microfoam techniques push resolution rates above 90% for spider veins, reticular veins, and small varicose veins.
What the Procedure Feels Like
Sclerotherapy is done in an office setting without anesthesia. You lie down, and the provider inserts a very fine needle directly into the target vein. Most people feel a mild stinging or burning sensation at the injection site that lasts a few seconds. Several veins can be treated in one session, so you may receive anywhere from a few to a dozen or more injections depending on how many veins are being addressed.
A typical session takes 15 to 30 minutes. You walk out of the office the same day and can return to most normal activities immediately, though you’ll be asked to avoid strenuous exercise for a short period.
Recovery and Compression
After treatment, you’ll wear compression stockings to keep pressure on the treated veins. This helps the collapsed walls stay sealed and reduces bruising and swelling. Research from the Annals of the Royal College of Surgeons of England found that high-compression stockings alone produce results comparable to more elaborate bandaging, so most providers now skip bandages entirely in favor of stockings.
The typical recommendation is to wear compression stockings continuously for the first 48 to 72 hours, then during the day for one to two weeks afterward. Walking is encouraged right away because it promotes blood flow through the deeper, healthy veins. Most people return to work the same day or the next.
When Results Appear
Treated veins often look worse before they look better. Bruising, mild swelling, and temporary darkening along the vein are normal in the first week or two. After that, the fading process begins.
Spider veins typically disappear within three to six weeks. Some very small spider veins vanish almost immediately after injection. Varicose veins take longer, up to three or four months, because there’s more tissue for the body to break down. The full effect unfolds gradually, and most people need two to four treatment sessions spaced several weeks apart to achieve near-complete results.
Possible Side Effects
The most common side effect is post-inflammatory hyperpigmentation, a brownish discoloration along the path of the treated vein. It happens because the body processes trapped blood and deposits iron pigment in the skin. In most cases this fades on its own over several months, though it can occasionally persist longer.
Telangiectatic matting is another well-known side effect: clusters of very fine, reddish new blood vessels that appear near the treatment site. This occurs in roughly 16% of patients. Matting usually resolves on its own within three to twelve months, though it sometimes requires additional treatment. Other common but minor reactions include temporary redness, tenderness, and small lumps of trapped blood that the body gradually clears.
Serious complications are rare but can include allergic reactions to the sclerosant, skin ulceration at the injection site, or blood clots in deeper veins.
Who Should Not Have Sclerotherapy
Certain conditions rule out sclerotherapy entirely. A known allergy to the specific sclerosant, an active infection (either widespread or at the treatment site), and a history of deep vein thrombosis are all absolute contraindications. The same applies to severe peripheral arterial disease, advanced connective tissue disorders, and anyone who has experienced a cardiovascular or neurological event after a previous sclerosant injection.
Pregnancy, breastfeeding, a strong history of allergic reactions, asthma, blood clotting disorders, and severely limited mobility are considered relative contraindications, meaning the procedure might still be done in some cases but carries additional risk that needs careful evaluation.
How It Compares to Other Vein Treatments
Sclerotherapy works best on spider veins and small to medium varicose veins, roughly those under 3 to 4 millimeters in diameter. For larger varicose veins, providers often recommend heat-based procedures that use laser or radiofrequency energy delivered through a catheter to seal the vein from the inside. These are typically reserved for the saphenous veins, the main superficial veins in the leg, while sclerotherapy handles their smaller tributaries and the web-like spider veins closer to the skin surface.
Surface laser treatment is another option for very small spider veins, particularly on the face, but it generally produces less consistent results on leg veins compared to sclerotherapy. For most people with cosmetically bothersome spider veins or mildly symptomatic small varicose veins, sclerotherapy remains the first-line treatment because of its high success rate, minimal downtime, and relatively low cost per session.