Sclerotherapy

Introduction

Sclerotherapy is a minimally invasive treatment used to close down unwanted veins — most often spider veins and varicose veins in the legs, and sometimes abnormal veins in other parts of the body. A doctor injects a special solution, called a sclerosant, directly into the vein. The solution irritates the inside wall of the vein, causing it to seal shut. Over weeks and months, the body breaks down the closed vein and reroutes blood flow through healthier nearby veins.

If you are reading this, you have probably already been told that sclerotherapy is one of the options for your veins, or you are weighing it against other treatments such as laser ablation or surgery. This article explains what sclerotherapy is, the different forms it takes, who it suits, how it is done, what recovery looks like, and what to expect in the months after. It does not replace a conversation with a vascular specialist, but it should help you walk into that conversation with clearer questions.

What Is Sclerotherapy?

Sclerotherapy comes from the Greek word skleros, meaning hard. The treatment works by deliberately hardening the inside of a problem vein so that it closes. After the vein closes, blood is redirected through other healthy veins, and the closed vein gradually shrinks and fades from view.

The sclerosant solution is injected through a very fine needle. The most commonly used agents internationally are polidocanol and sodium tetradecyl sulphate (STS). For very small spider veins, a concentrated salt solution (hypertonic saline) is sometimes used. The choice of agent, its concentration, and the volume injected depend on the size, depth, and type of vein being treated.

Sclerotherapy has been used for decades and is one of the standard treatments for chronic venous disease in the legs. The Society for Vascular Surgery (SVS), the American Venous Forum (AVF), the European Society for Vascular Surgery (ESVS), and the UK’s NICE guidance all describe sclerotherapy as an established option within a range of treatments for varicose veins and related conditions.

Why Is Sclerotherapy Performed?

Sclerotherapy is used to treat veins that are not working properly, are visible and unwanted, or are causing symptoms. The main reasons it is performed are:

• Spider veins (telangiectasias): tiny red, blue, or purple veins close to the skin surface, often on the thighs, calves, ankles, or face. These are usually a cosmetic concern but can also cause burning or itching.
• Reticular veins: slightly larger, bluish veins under the skin, often a feeder for spider vein clusters.
• Varicose veins: larger, rope-like veins that bulge under the skin and may ache, throb, swell, or feel heavy, especially after standing.
• Residual or recurrent veins: veins that remain or come back after another vein treatment such as surgery or thermal ablation.
• Venous malformations: abnormal clusters of veins that some people are born with, including certain malformations in children and young adults.
• Haemorrhoids and other internal varicose-type veins: in selected cases, sclerotherapy is used inside the rectum or in pelvic veins.

Whether sclerotherapy is suitable depends on the type and size of the vein, where it sits in the leg, the overall pattern of venous disease, and your general health. Vascular specialists usually start with a clinical examination and a duplex ultrasound scan of the leg veins. The scan shows which veins are leaking (refluxing), which are blocked, and which deeper veins are healthy.

People who are commonly considered good candidates include those with:

• Cosmetic spider veins or small reticular veins.
• Varicose veins not arising from a major underlying reflux in the saphenous vein system, or varicose tributaries left over after the main trunk has been treated.
• Smaller varicose veins where surgery or thermal ablation may be more than is needed.
• Recurrent veins after previous treatment.
• Selected venous malformations, often managed by interventional radiologists or vascular specialists with specific expertise.

Sclerotherapy is usually not recommended, or used only with great caution, in people who:

• Are pregnant or breastfeeding (most specialists postpone elective treatment).
• Have a history of deep vein thrombosis (DVT), pulmonary embolism, or known clotting disorders, unless carefully assessed.
• Have an active skin infection over the treatment area.
• Are immobile or bedbound, since walking after treatment is part of how the leg recovers safely.
• Have a known allergy to the sclerosant being considered.
• Have severe arterial disease in the legs.
• Have a known right-to-left heart shunt (such as a large patent foramen ovale) when foam sclerotherapy is being considered — this is a specific situation discussed with the specialist.

Sclerotherapy is not a single technique. The form used depends mainly on the size of the vein and how deep it lies.

Liquid Sclerotherapy

This is the original and simplest form. A liquid sclerosant is injected directly into the vein through a fine needle. Liquid sclerotherapy is most commonly used for small surface veins — spider veins and small reticular veins. The doctor can see the vein clearly, so no imaging is needed during the injection.

Foam Sclerotherapy

For larger varicose veins, the same sclerosant can be mixed with air or a physiological gas to create a foam. The foam displaces blood inside the vein and stays in contact with the vein wall for longer, which makes it more effective in larger veins. Foam sclerotherapy is widely used for varicose veins that are too big for liquid sclerotherapy but where surgery or thermal ablation may not be required, or as part of a combined treatment plan. International guidelines, including those from the ESVS and NICE, describe foam sclerotherapy as one of the main minimally invasive options for varicose veins.

Ultrasound-Guided Sclerotherapy

When the problem vein is deeper under the skin and cannot be seen clearly — for example, parts of the great or small saphenous vein, or perforator veins — the doctor uses a handheld ultrasound probe to guide the needle and confirm correct placement of the sclerosant. Ultrasound-guided foam sclerotherapy (sometimes shortened to UGFS) is commonly used for larger varicose veins and for veins that have come back after earlier treatment.

Microsclerotherapy

This is the term used for sclerotherapy of very tiny spider veins, usually with very low concentrations of sclerosant injected through extremely fine needles. The principle is the same; the equipment and dosing are scaled down.

Alternatives to Sclerotherapy

Sclerotherapy is one of several treatments for vein problems. The choice between them depends on the type, size, and pattern of disease, the symptoms, and individual preference. Major societies recommend that all reasonable options be discussed.

• Compression stockings: medical-grade graduated compression stockings help control symptoms of varicose veins and may be tried first, especially when symptoms are mild. They do not close the veins; they manage the condition.
• Endovenous thermal ablation: includes endovenous laser ablation (EVLA) and radiofrequency ablation (RFA). A thin catheter is placed inside the diseased vein and heat is delivered to close it. These techniques are first-line for many cases of saphenous vein reflux in current NICE and ESVS guidance.
• Non-thermal, non-tumescent (NTNT) techniques: include mechanochemical ablation and cyanoacrylate glue closure. These close the vein without heat and without the need for multiple anaesthetic injections along the vein.
• Surgical stripping and ligation: the traditional open surgery for varicose veins. Still used in selected cases, but largely replaced by minimally invasive options for most patients.
• Phlebectomy (ambulatory phlebectomy): bulging surface varicose veins are removed through tiny skin nicks, often combined with ablation or sclerotherapy of the underlying source vein.
• Lifestyle measures: regular walking, leg elevation, weight management, and avoiding long periods of standing still can ease symptoms but do not reverse existing varicose veins.
• Laser treatment of the skin surface: for very small facial spider veins or for patients who cannot tolerate needles, surface laser is sometimes used as an alternative to sclerotherapy. For leg spider veins, sclerotherapy is generally considered the more effective option, though practice varies.

Sclerotherapy is often used alongside other treatments rather than instead of them. For example, a saphenous vein may be closed with laser or radiofrequency ablation, while the remaining branch varicosities and spider veins are treated with sclerotherapy in follow-up sessions.

Preparing for Sclerotherapy

Sclerotherapy is an outpatient procedure. There is no general anaesthetic, no overnight stay, and no need to fast in most cases. Preparation is usually straightforward, but a few practical points matter.

Before the appointment:

• You will usually have a consultation and a duplex ultrasound to map the veins before any treatment is planned.
• Tell your doctor about all medications and supplements you take, particularly blood thinners (such as aspirin, clopidogrel, warfarin, or direct oral anticoagulants), hormone therapies, and any history of clotting problems.
• Mention any allergies, especially to medications or to local anaesthetics.
• If you have ever had a deep vein thrombosis, a pulmonary embolism, a stroke, migraine with aura, or have a known hole in the heart, mention this. It can change the choice of agent and technique, especially for foam sclerotherapy.
• You will usually be asked to bring or buy medical-grade compression stockings to wear after treatment. The specialist will advise on strength and length.

On the day:

• Do not shave or apply lotion, oil, or self-tanner to your legs on the day of treatment.
• Wear loose, comfortable clothing. Shorts or a skirt make access easier, and you will often change into a gown.
• Eat a normal light meal beforehand; sclerotherapy is not done on an empty stomach.
• You can usually drive yourself home, but ask your specialist — some prefer that patients arrange transport, especially after larger treatment sessions.

What Happens During Sclerotherapy

1. Positioning: You lie on a treatment table, usually on your back with the legs slightly raised, or on your front for veins on the back of the leg. The skin is cleaned with antiseptic.
2. Marking and imaging: The doctor may mark the veins with a skin pen while you stand, since varicose veins are most visible when standing. For ultrasound-guided sclerotherapy, the probe is placed on the skin to visualise the deeper vein.
3. Injection: A very fine needle is inserted into the vein and a small amount of sclerosant is injected. You may feel a small sting or mild burning at the injection site. The doctor moves along the leg, treating several segments in one session. For foam sclerotherapy, the foam is prepared at the bedside immediately before injection.
4. Compression: After each injection, the doctor presses on the vein and may apply cotton pads and tape over the site. Once treatment is complete, a compression stocking is fitted to the leg.
5. Walking afterwards: You will be asked to walk for at least 15 to 30 minutes immediately after the session, and to keep moving regularly in the following days. Walking is an important part of safe recovery because it keeps blood moving through the deep veins and reduces the risk of clots.

Most patients tolerate the procedure well. There is no general anaesthetic, and local anaesthetic is rarely needed for sclerotherapy itself, since the needles are very fine.

How Many Sessions Are Needed?

Sclerotherapy is almost always done as a course of sessions rather than a single treatment. The number depends on the extent of disease:

• Small clusters of spider veins may need one to three sessions.
• Extensive spider and reticular veins on both legs may need three to six sessions or more.
• Larger varicose veins may need repeated sessions to fully close all branches, sometimes combined with another procedure.

Sclerotherapy is sometimes called a “lunchtime procedure” because most people return to normal activities the same day. Even so, what happens in the days and weeks after the session matters for the final result.

The First Few Days

• Compression stockings: Specialists typically advise wearing a compression stocking continuously for the first 24 to 48 hours, then during the daytime for a further one to three weeks. The exact regimen varies by vein size and by clinic.
• Walking: Frequent short walks are encouraged. Avoid long periods of sitting or standing still.
• Avoid: hot baths, saunas, steam rooms, hot tubs, and very hot showers for about a week. Heat dilates surface veins and may worsen bruising and pigmentation.
• Sun exposure: Keep the treated areas out of direct sunlight for several weeks, or cover them, to reduce the risk of brown skin discolouration over the treated veins.
• Exercise: Gentle walking is encouraged from day one. Heavy gym work, running, and high-impact exercise are usually paused for a few days to a week, depending on the size of veins treated.
• Flying: Long-haul flights are usually best avoided in the first two to four weeks after treatment of larger veins, because of the small additional clotting risk. Specialists advise on individual timing.

What You Will See on the Skin

It is normal to see some of the following in the first weeks after sclerotherapy:

• Bruising around the injection sites, fading over one to three weeks.
• Small raised, pink, itchy patches near treated veins.
• Lumps along the line of treated varicose veins. These are trapped clotted blood inside the closed vein (called trapped coagulum) and are not the same as a DVT. They are common, harmless, and usually settle, though they can take weeks or months to soften. The doctor may release them with a small needle puncture at a follow-up visit to speed up resolution and reduce pigmentation.
• Brown or tan lines over treated veins (post-inflammatory hyperpigmentation). These fade in most people over several months, but in some can persist longer.
• A faint network of very fine new red vessels (called matting) near the treatment area in some people. This may fade on its own or require further treatment.

When You Will See the Final Result

Sclerotherapy does not deliver an instant result. The treated veins fade gradually as the body reabsorbs them.

• Spider veins typically show clear improvement at three to six weeks, with full effect at three to four months.
• Larger varicose veins may take three to six months to soften, fade, and become less visible.
• Follow-up appointments are usually scheduled at four to six weeks to assess response and plan further sessions if needed.

Risks and Complications

Sclerotherapy is generally considered a safe procedure when performed by trained specialists, but no medical treatment is risk-free. Major societies recommend that risks are discussed clearly before consent.

Common, usually minor:

• Bruising, mild stinging or burning at injection sites, temporary itching.
• Skin discolouration (brown lines over treated veins) that fades over months.
• Trapped clotted blood in closed veins, sometimes needing a small drainage at follow-up.
• Telangiectatic matting — fine new vessels near the treatment site.

Less common:

• Small skin ulcers at the injection site, particularly if sclerosant leaks outside the vein. These heal but can leave a scar.
• Allergic reactions to the sclerosant. True severe allergy is rare but possible.
• Inflammation of the treated vein (superficial thrombophlebitis), causing a tender red cord under the skin that settles with anti-inflammatory measures.

Rare but important:

• Deep vein thrombosis (DVT) — a clot in the deep leg veins. This is uncommon after sclerotherapy and is one of the reasons walking and compression are emphasised.
• Pulmonary embolism — a clot travelling to the lungs. Very rare.
• Visual disturbances, migraine-like symptoms, or, exceptionally rarely, neurological symptoms after foam sclerotherapy. These are usually short-lived and most often reported in people with a right-to-left heart shunt. This is why screening questions about migraine with aura and known heart shunts are asked.
• Accidental injection into a small artery, which can cause skin or tissue damage. This is rare with experienced operators and ultrasound guidance where appropriate.

You should seek urgent medical attention after sclerotherapy if you develop sudden severe leg swelling and pain, sudden shortness of breath, chest pain, coughing up blood, a sudden severe headache, or new neurological symptoms such as weakness or speech difficulty.

Life After Sclerotherapy

Will the Veins Come Back?

The veins that are successfully treated do not “come back” in the sense of reopening, in most cases. However, varicose vein disease is a chronic condition driven by valve weakness that does not go away. New varicose veins or spider veins may appear over the years, either in untreated areas or as the disease progresses elsewhere in the venous system. Follow-up duplex ultrasound is used to detect this, and further sessions of sclerotherapy or other treatments can be planned when needed.

Recurrence is more common in people with:

• A strong family history of varicose veins.
• Multiple pregnancies after treatment.
• Jobs that involve long periods of standing.
• Significant weight gain.
• Underlying reflux in the saphenous system that was not addressed.

Reducing the Chance of New Veins

Although you cannot change your genes, several measures help slow the progression of venous disease:

• Regular walking and calf-muscle activity.
• Avoiding long periods of standing or sitting without movement; taking breaks to stretch and walk.
• Elevating the legs above heart level for short periods at the end of the day if the legs feel heavy.
• Maintaining a healthy weight.
• Wearing graduated compression stockings during long flights, long working days on your feet, or pregnancy, on the advice of your doctor.

Follow-Up Care

A typical follow-up plan looks like this:

• Review at four to six weeks after each session to check progress and plan further treatment.
• A final review at three to six months to assess the full result.
• Longer-term review (sometimes annually) for people with extensive disease, or as advised by the specialist.

Frequently Asked Questions

Is sclerotherapy painful?

Most people describe sclerotherapy as mildly uncomfortable rather than painful. The needles are very fine, and the main sensation is a brief stinging or burning at each injection site. Larger veins treated with foam may cause a stronger cramping sensation for a few seconds. No general anaesthetic is needed.

How long do the results last?

Veins that close after sclerotherapy generally stay closed. The body absorbs them over months. However, new varicose or spider veins can develop over time, especially in people with a genetic tendency. Some patients return for top-up sessions every few years.

Can sclerotherapy treat large varicose veins on its own?

For larger varicose veins arising from saphenous vein reflux, current NICE and ESVS guidance generally favours thermal ablation (laser or radiofrequency) or non-thermal ablation as first-line treatment. Foam sclerotherapy is one of the established alternatives and is also commonly used for branch varicosities and recurrent veins. The right combination for any individual case is a clinical decision based on duplex ultrasound findings.

Is sclerotherapy safe during pregnancy?

Elective sclerotherapy is generally postponed until after pregnancy and breastfeeding. Varicose veins that worsen in pregnancy often improve in the months after delivery, and treatment decisions are usually made several months postpartum.

How soon after treatment can I exercise?

Gentle walking is encouraged from the same day. Most specialists advise pausing high-impact exercise, heavy weightlifting, and intense gym sessions for a few days to a week. Swimming is usually paused while injection sites heal, typically for about a week. Your specialist will give specific guidance based on the size of the veins treated.

Will I need to wear compression stockings all the time?

Compression stockings are usually worn continuously for the first 24 to 48 hours, then during the daytime for one to three weeks, depending on the size of veins treated. Long-term daily use of stockings is not usually required after spider vein treatment, but may be advised for people with ongoing venous disease.

Can men have sclerotherapy?

Yes. Although varicose and spider veins are more often reported in women, men also develop them and are treated with the same techniques.

What happens if a session does not fully close a vein?

Partial closure is not unusual, especially in larger veins. The vein is usually re-treated at a follow-up session, sometimes with a different concentration or with foam instead of liquid. This is one of the reasons sclerotherapy is planned as a course rather than a single visit.

Does sclerotherapy leave scars?

Sclerotherapy does not involve cuts, so it does not leave surgical scars. Tiny needle marks heal without trace in most people. Brown skin discolouration over treated veins is more common than scarring and usually fades over months.

Are there any veins that should not be treated?

Yes. The deep veins of the leg, which carry most of the blood back to the heart, must not be closed. A duplex ultrasound before treatment confirms that the deep veins are working normally and identifies which surface veins can be safely treated. This is one reason an ultrasound assessment is considered standard before sclerotherapy for varicose veins.

Conclusion

Sclerotherapy is a well-established, minimally invasive treatment for spider veins and many varicose veins. It is performed in clinic, uses fine-needle injections of a sclerosant solution, and typically requires several short sessions for the full result. Variants such as liquid, foam, and ultrasound-guided sclerotherapy allow specialists to treat veins of different sizes and depths. Recovery is usually quick, with compression stockings and walking forming the core of aftercare, and final cosmetic improvement appearing over three to six months.

Sclerotherapy is one option within a wider menu of treatments for venous disease that also includes endovenous thermal ablation, non-thermal techniques, phlebectomy, and surgery. The choice between these — and the question of whether sclerotherapy alone, sclerotherapy combined with another procedure, or a different approach altogether is most suitable — is a clinical decision made together with a vascular specialist after a proper assessment, including duplex ultrasound. With that assessment in hand, the questions in this article should help you understand the path your specialist describes and make a confident, informed choice about your care.