What is sclerotherapy?
Sclerotherapy is an injection treatment used mainly for spider veins and small reticular veins, most often on the legs. A clinician injects a sclerosant into the unwanted vein. The solution damages the inner lining, causing the vessel to close. Over time, the body gradually absorbs the treated vein and blood is redirected through other healthy vessels.
It is one of the standard treatments for small visible leg veins. It is not the same as treating significant varicose-vein reflux or chronic venous disease.
Which veins can sclerotherapy treat?
It is commonly used for:
- telangiectasias or spider veins — very small red, blue or purple surface vessels;
- reticular veins — slightly larger blue-green veins beneath the skin;
- selected small varicose tributaries, depending on the underlying venous anatomy.
Facial vessels are usually approached differently. Vascular lasers are often preferred because injecting tiny facial veins carries different anatomical and cosmetic considerations.
Do I need an ultrasound before treating spider veins?
Not everyone with a few isolated spider veins needs an ultrasound. But visible surface veins can sometimes be fed by deeper reflux.
If you also have larger varicose veins, leg swelling, aching, heaviness, skin changes, recurrent veins or a history suggesting venous disease, a proper vascular assessment should come before cosmetic injections. Treating only the surface veins while ignoring significant reflux can lead to disappointing recurrence.
What is injected during sclerotherapy?
Common sclerosants include polidocanol and sodium tetradecyl sulfate. Concentration and whether the solution is used as a liquid or foam depend on the vein size and clinical situation. Hypertonic glucose is used in some countries and protocols.
Stronger is not automatically better. A 2023 network meta-analysis found that greater sclerosant potency tended to come with more adverse effects. The aim is to use enough treatment to close the target vessel while minimising unnecessary inflammation and skin injury.
What happens during a sclerotherapy session?
The clinician maps the visible veins and places very fine needles into the target vessels. Small amounts of sclerosant are injected. You may feel a brief sting, burning or cramping sensation.
A session can involve multiple injections. Compression may be applied afterwards depending on the vein type and protocol. Most people can walk immediately and return to ordinary light activity the same day.
How quickly do spider veins disappear?
They do not usually vanish immediately. Treated vessels often look darker or more obvious before they fade.
Small spider veins may improve over several weeks, while larger reticular veins can take a few months. More than one session is common. Long-term follow-up also shows an important distinction: a successfully closed vein may stay closed, but new veins can develop because the underlying tendency to form them remains.
How effective is sclerotherapy?
Sclerotherapy has a strong evidence base for leg telangiectasias and reticular veins. A 2023 systematic review and network meta-analysis of 19 studies found several sclerosants to be effective, while also showing that laser can perform particularly well for very small telangiectasias.
Newer randomized studies continue to show meaningful vessel clearance with standard polidocanol sclerotherapy. No single technique is best for every vessel. Very fine red vessels may respond better to a vascular laser, while feeding reticular veins often respond well to injection treatment.
What are the common side effects?
Bruising, tenderness, swelling and temporary firmness along a treated vein are common. Two cosmetic effects deserve special mention:
- Hyperpigmentation: brown staining can appear along the treated vessel as blood pigments are cleared. A systematic review found highly variable rates depending on polidocanol concentration and vein type, from low single digits to much higher percentages in some studies. Most staining fades, but it can persist for months.
- Telangiectatic matting: a fine network of new tiny vessels can appear near the treated area. It often improves gradually but can be frustrating.
These are not necessarily signs that the vein has been treated incorrectly, but technique, concentration and underlying venous pressure matter.
What rare complications should I know about?
Serious complications are uncommon, but sclerotherapy is still a medical procedure.
Rare risks include skin ulceration or necrosis, allergic reaction, superficial thrombophlebitis, deep-vein thrombosis, nerve irritation and neurological symptoms. Transient visual disturbance has been reported particularly with foam sclerotherapy; older large series and reviews estimated it at roughly 0.09% to 2%, with persistent visual injury much rarer.
International consensus lists acute venous thromboembolism, severe acute illness or infection, critical limb ischaemia and known serious hypersensitivity to the sclerosant among important contraindications.
How should I prepare?
Tell the treating clinician about previous blood clots, clotting disorders, pregnancy, migraine with aura, cardiovascular or neurological history, allergies and medications that affect bleeding or clotting. Do not stop prescribed medication without medical advice.
A good consultation should also establish whether your concern is purely cosmetic or whether symptoms suggest underlying venous disease.
What should I do after sclerotherapy?
Walking is usually encouraged. Your clinician may recommend compression stockings for a period depending on the vein size and treatment method. Avoiding prolonged immobility is sensible.
Advice about vigorous exercise, hot baths, saunas and sun exposure varies by protocol. Follow the instructions for the sclerosant and veins actually treated rather than a generic clinic handout.
Seek urgent medical assessment for significant calf swelling, chest pain, shortness of breath, severe neurological symptoms or rapidly worsening pain.
Is sclerotherapy better than laser for spider veins?
Neither is universally better.
For very small superficial telangiectasias, particularly vessels that are difficult to cannulate, vascular laser can be an excellent option. Sclerotherapy is highly effective for many leg spider veins and especially useful when reticular feeding veins are present.
The most sensible choice is based on vessel diameter, colour, depth, skin type and whether there is underlying venous reflux — not on which machine or injectable a clinic happens to sell.
