What Is Sclerotherapy?

Picture yourself in the clinic chair, leg resting on the couch, while the clinician leans in with a very fine needle. That, in essence, is sclerotherapy — an injection treatment that closes off unwanted veins from the inside, most often the visible varicose and spider veins in the legs. There's no operating theatre and no general anaesthetic in the usual picture; it's an outpatient treatment done in a clinic room. The video at the top of this page, "Sclerotherapy to remove leg veins." (about nine minutes, from the Dermatology Center at UC Irvine), shows foam sclerotherapy being used on leg veins, so you can watch the pace and setting of a real appointment before reading on.

Before anything is injected

Your visit usually starts with an assessment, not a needle. The clinician examines your legs, asks about symptoms such as aching, heaviness or swelling, and goes over your medical history. For larger varicose veins, an ultrasound scan is often part of the work-up, because it shows which deeper veins are feeding the surface ones — treating only what you can see, without that map, tends to disappoint. This is also the moment to mention previous vein treatments, any history of blood clots, and medicines you take, since all of that shapes whether sclerotherapy is the right tool or whether another option fits better. Our broader guide to how varicose veins are treated sets sclerotherapy alongside the other approaches your clinician might discuss.

In the chair — the injections themselves

Once you're settled, the skin is cleaned and the solution is injected directly into the vein through a fine needle. The liquid irritates the vein's inner lining, which makes the walls stick together and seals the vein shut. For bigger veins, the same kind of solution may be mixed into a foam first — foam spreads further and stays in contact with the vein wall longer, which is why the anchor video on this page is a foam treatment. You may feel small pinpricks and, occasionally, a brief mild stinging as each injection goes in; most appointments involve several injections, and the session itself is usually over in well under an hour. Where the vein isn't visible from the surface, ultrasound guides the needle instead — you can see that variation in this ultrasound-guided sclerotherapy video, which follows the same treatment with the scan screen directing each step.

The weeks afterwards — what changes, and when

A treated vein doesn't vanish on the day. Once sealed, it gradually fades as the body absorbs it, and blood simply reroutes through healthier veins nearby. Spider veins typically fade over a few weeks; larger varicose veins can take longer, and more than one session is commonly needed — your clinician should set that expectation honestly at the first visit rather than promising a single-appointment fix. You'll usually be asked to wear compression stockings for a period afterwards and to walk regularly, both of which help the treated veins stay closed while you heal. Bruising along the treated vein, mild itching, and temporary brownish skin staining are all commonly reported along the way and usually settle; a treated area that becomes increasingly painful, hot, or swollen deserves a prompt call to the clinic rather than a wait-and-see approach. And because a new leg swelling always deserves proper assessment on its own terms, our explainer on deep vein thrombosis (blood clots) covers the symptoms that should never be dismissed as "just healing."

What sclerotherapy can't do

It helps to be clear about the limits. Sclerotherapy closes the veins that are treated; it doesn't change the underlying tendency to form varicose veins, so new ones can appear over time and later top-up treatment is not unusual. Very large veins, or veins driven by a faulty deeper valve that needs a different fix, may be better served by a thermal or surgical procedure — which is exactly why the assessment and ultrasound mapping come first. Think of it as one well-established tool in the vein clinic's kit: excellent for the right veins, and a poor substitute for a proper diagnosis when the picture is more complicated.

Frequently Asked Questions

Does sclerotherapy hurt?

Most people describe a series of small pinpricks and sometimes a brief mild sting as the solution goes in. It's uncomfortable rather than painful for most, and no anaesthetic is usually needed. Tell your clinician if you find it more than you expected — pacing and technique can be adjusted.

How many sessions will I need?

That depends on how many veins are being treated and how they respond. A single session can cover a number of veins, but many people need more than one appointment, spaced some weeks apart. Your clinician should give you a realistic estimate after the assessment, not before it.

Is the foam version different from regular sclerotherapy?

The goal is the same — closing the vein from inside. In foam sclerotherapy the solution is mixed with a small amount of gas to make a foam, which displaces blood in the vein and keeps the solution against the vein wall longer. It's often chosen for larger veins, sometimes with ultrasound guidance, as the videos on this page show.

Can I go straight back to normal activities?

Generally, yes — walking is encouraged from the same day, and most people return to work and everyday routines quickly, wearing compression stockings as advised. Strenuous exercise and long-haul travel are usually best discussed with your clinic first, since advice varies with the size of the veins treated.

Will the veins come back?

The treated vein itself is closed permanently, but the tendency to develop varicose veins remains, so new veins can form over the years. If that happens, further treatment can usually be offered after a fresh assessment.

References & further reading

• MedlinePlus — Varicose Veins: https://medlineplus.gov/varicoseveins.html
• National Heart, Lung, and Blood Institute (NHLBI) — Varicose Veins: https://www.nhlbi.nih.gov/health/varicose-veins
• RadiologyInfo (RSNA/ACR) — Sclerotherapy: https://www.radiologyinfo.org/en/info/sclerotherapy

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Dr. Mohamed Ibrahim, MD, PhD

Physician-scientist · Founder, MedicalVideos.com

Dr. Ibrahim founded MedicalVideos.com in 2007 to make medical and surgical education freely accessible to students, clinicians, and patients.

Last reviewed: 11/10/26

This article is for general education only and is not medical advice. It does not replace consultation with a qualified clinician. Whether sclerotherapy is appropriate for you, and which technique fits your veins, can only be decided by your own care team after assessment and, where needed, ultrasound examination.