Sclerotherapy

Sclerotherapy is often introduced as an injection that removes spider veins.

The injection is real.

The word removes is less precise.

A sclerosant is injected into a selected vein and deliberately damages its endothelial lining. The treated vein then thromboses, contracts and gradually becomes fibrotic so that blood is redirected through other functioning venous pathways.

Over time, the treated vessel becomes much less visible or may no longer be clinically apparent.

This makes sclerotherapy particularly useful for selected telangiectasias, reticular veins and larger superficial venous tributaries.

But the visible vein is only the final structure that the patient sees through the skin.

The important clinical question is what venous system is feeding it.

So I do not begin with the syringe. I begin by deciding whether this is an isolated cosmetic surface vein, part of a reticular network or the visible expression of a larger pattern of venous reflux that needs a different level of assessment.

A spider vein is a vessel, not simply a red line on the skin

Telangiectasias are very small superficial vessels, usually less than approximately one millimetre in diameter.

Reticular veins are larger subdermal vessels, often blue or green, that can feed networks of smaller telangiectasias.

Varicose veins are larger superficial veins that have become dilated and tortuous and may be associated with underlying venous reflux.

These categories are connected but not identical.

The difference matters because the optimal sclerosant formulation, concentration, injection method and need for ultrasound assessment change with vessel size and venous anatomy.

The visible vein tells me where the problem appears.

It does not always tell me where the venous problem begins.

Not every cosmetic spider vein requires a full venous ultrasound

This is one area where more investigation is not automatically better medicine.

Current vascular guidelines do not recommend routine duplex-ultrasound examination for every asymptomatic patient whose only finding is uncomplicated cosmetic telangiectasia or small reticular veins.

Unnecessary imaging can discover incidental reflux and lead to treatment of veins that did not need ablation simply because an abnormality was visible on a scan.

That changes when symptoms or larger venous disease are present.

Significant pain, burning, bleeding, swelling, heaviness, larger varicosities or other signs of chronic venous disease can justify duplex examination because the treatment plan may need to address a deeper or more proximal source.

The amount of investigation should follow the clinical question just as the amount of treatment should.

Larger varicose veins change the diagnostic threshold

A patient with obvious varicose tributaries, leg heaviness, edema or other symptoms may have superficial truncal reflux or additional venous pathology.

In that setting, simply injecting every visible surface branch can improve appearance temporarily while leaving the haemodynamic mechanism underneath untreated.

The correct sequence may involve ultrasound assessment and treatment of an incompetent truncal vein, selected tributaries or both.

Sclerotherapy can remain part of that plan.

It simply should not become the whole plan because it is capable of making individual vessels disappear.

Sclerotherapy works by intentionally injuring the inside of the vein

Common sclerosants such as polidocanol and sodium tetradecyl sulfate act as detergent agents.

When appropriately delivered into a vein, they disrupt endothelial cell membranes.

This initiates thrombosis and subsequent organisation of the treated vessel.

Over time, fibrosis and resorption reduce the visible venous channel.

The objective is controlled endothelial destruction.

This is why concentration and volume matter.

The treatment needs enough sclerosant to damage the target vein without allowing unnecessary exposure of surrounding tissue or the broader circulation.

Concentration should follow vessel diameter

A very small telangiectasia and a larger reticular vein do not require the same chemical dose.

Using a concentration appropriate for a larger vessel in a tiny superficial vein can increase inflammation, pigmentation and tissue injury without producing a better cosmetic result.

Using too little in a larger vessel can produce incomplete sclerosis and recurrence.

The strongest sclerosant is not the best sclerosant.

The correct concentration is the minimum concentration capable of closing the vessel being treated.

This is one of the most direct examples of precision over aggressiveness in aesthetic medicine.

Polidocanol and sodium tetradecyl sulfate are both established sclerosants

These are among the most widely used detergent sclerosants internationally.

Both can effectively treat selected superficial veins when the concentration and method are appropriate.

Comparative evidence suggests broadly similar efficacy for many small-vessel applications, with polidocanol often associated with less injection discomfort and sodium tetradecyl sulfate sometimes producing more pigmentation or local irritation at comparable clinical applications.

I do not regard that as proof that one agent is universally better.

The vessel, concentration, product availability and operator experience all matter.

Liquid and foam sclerotherapy have different physical behaviour

In liquid sclerotherapy, the sclerosant mixes directly with blood as it enters the vessel.

Foam is created by mixing the sclerosant with gas, producing microbubbles that displace blood and increase contact between the active drug and the venous wall.

This can make foam particularly useful in larger reticular veins, tributaries and other selected venous targets.

The same physical advantage is not necessarily required for the smallest surface vessels.

Foam also introduces its own adverse-effect profile, including transient visual or migraine-like symptoms that are reported more often than with simple liquid treatment.

More contact is a useful property only when the vein needs it.

Foam is not simply stronger liquid

The drug itself may be the same.

The gas changes how it interacts with the vein.

Because foam displaces blood, a relatively small quantity can expose a larger surface area of endothelial tissue.

This can increase efficiency in the right vessel.

It also means foam volume and systemic distribution deserve attention.

I do not use foam as an automatic upgrade simply because the technology sounds more sophisticated.

Feeder veins can determine whether small spider veins keep returning

A cluster of fine telangiectasias can be connected to a larger reticular feeder vein beneath the skin.

If only the smallest red vessels are injected, the deeper network may continue supplying the visible area.

This can contribute to incomplete clearance or recurrence.

In selected cases, treating the reticular component first or during the same treatment plan makes the cosmetic result more coherent.

The principle is the same as treating anatomy before surface labels.

The smallest visible branch is not necessarily the most important vessel in the network.

More injections are not automatically more complete treatment

A leg can contain hundreds of small vessels.

The temptation is to inject as many as possible during one session.

But sclerosant dose accumulates, tissue inflammation accumulates and the treated network becomes more difficult to assess immediately.

I prefer staged treatment when that gives better control.

The first session can reduce the dominant vessels.

After healing, the residual pattern becomes easier to see.

Some small veins may no longer require treatment once their feeder has closed.

Hyperpigmentation is one of the most common cosmetic trade-offs

Brown staining can develop along treated veins after sclerotherapy.

This is often related to inflammation, thrombosis and deposition of iron-containing blood-breakdown products within surrounding tissue.

Most staining gradually improves.

It can sometimes persist for months and occasionally longer.

This is particularly important because a patient seeking treatment for a visible vein may temporarily exchange a blue or red line for a brown one.

A technically closed vein is not yet a complete aesthetic result if its footprint remains visible in another colour.

The possibility should therefore be discussed before treatment rather than introduced afterwards as an unexpected cosmetic phase.

Trapped blood can make a successfully treated vein look worse before it looks better

After the venous wall closes, blood can remain trapped within portions of the treated vessel.

The vein may become firm, dark and tender.

This is not necessarily evidence that sclerotherapy failed.

In selected situations, evacuation of trapped coagulum through microthrombectomy can reduce discomfort and may reduce persistent pigmentation.

The important distinction is between an expected local thrombotic response and complications extending beyond the intended superficial vein.

Telangiectatic matting is not simply treatment failure

Some patients develop a fine network of new red vessels around a treated area.

This is known as telangiectatic matting.

It may relate to local inflammatory and haemodynamic responses and is more likely in certain patients and treatment situations.

Immediately injecting every new vessel can sometimes perpetuate the cycle.

I first want to reassess the area, residual feeder veins and time since treatment.

Some matting improves spontaneously.

Not every visible vessel after sclerotherapy requires another injection immediately.

Skin necrosis is uncommon and fundamentally different from ordinary bruising

Small bruises and local inflammation are expected possibilities.

Skin necrosis reflects unintended tissue ischemia or direct sclerosant injury.

It can follow extravascular injection, excessive superficial exposure, vascular compromise or, in rare circumstances, arterial involvement.

The result can be ulceration and permanent scarring.

This is why severe pain, blanching or an unusual vascular pattern during injection needs immediate attention rather than being dismissed as a stronger-than-average sting.

Intra-arterial injection is rare and potentially severe

Sclerotherapy is intended for veins.

Accidental arterial injection can cause vasospasm, thrombosis and tissue ischemia with potentially serious consequences.

International guidelines published in 2024 emphasise that suspected intra-arterial injection requires urgent vascular assessment and, in severe cases, endovascular treatment.

This risk is uncommon.

It explains why knowledge of vascular anatomy, injection response and appropriate ultrasound use matter even in a treatment frequently described as a cosmetic injection.

Deep-vein thrombosis is uncommon but belongs in the consent discussion

The intended clotting process should remain confined to the superficial vessel being treated.

Thrombus extension into the deep venous system is a recognised complication, particularly in treatment of larger veins and more extensive foam procedures.

Pulmonary embolism is rarer but possible.

Personal thrombotic history, hypercoagulable states, immobility and other VTE risk factors therefore matter before treatment.

The fact that a spider-vein injection is performed through a very small needle does not make the patient’s coagulation history irrelevant.

Pregnancy and recent thrombotic risk change the threshold

Pregnancy, postpartum physiology and other hypercoagulable states alter venous and thrombotic risk.

Modern international consensus treats several of these situations as relative contraindications requiring risk–benefit assessment rather than routine cosmetic treatment.

For purely aesthetic veins, there is generally little reason to force an elective intervention into a period in which venous physiology is temporarily altered and the cosmetic pattern may change again afterwards.

Waiting is often the more coherent treatment decision.

A known sclerosant allergy is an obvious reason to change method

Allergic reactions are uncommon but can occur.

Severe hypersensitivity is rare.

A known hypersensitivity to the intended sclerosant is an absolute contraindication in contemporary consensus guidance.

For selected very small telangiectasias, transcutaneous vascular laser can provide an alternative when sclerosant allergy, needle phobia or previous sclerotherapy failure makes injection less appropriate.

Visual symptoms after foam sclerotherapy deserve accurate explanation

Transient visual disturbances, headache and migraine-aura-like symptoms have been described particularly after foam procedures.

They are uncommon and usually resolve.

Right-to-left cardiac shunting has been investigated as one possible factor in some neurological events, although the mechanisms are complex.

I do not describe every brief visual disturbance as a stroke.

I also do not dismiss new neurological symptoms following treatment as a normal cosmetic reaction.

The symptom determines the level of assessment.

Stroke after sclerotherapy is very rare, but rarity does not justify pretending it cannot occur

Serious neurological complications have been reported in the literature, particularly in association with foam procedures.

The absolute risk is low.

This should keep the discussion proportional.

Sclerotherapy has a long clinical history and an overall favourable safety profile when appropriately performed.

The correct message is therefore not that foam sclerotherapy is dangerous.

It is that an apparently small venous procedure interacts with the circulation and therefore deserves genuine medical screening and technique.

Compression can improve the result after microsclerotherapy

Compression stockings are commonly used after treatment of spider and reticular veins.

Clinical trials and guidelines support compression after liquid microsclerotherapy because it can improve clinical response and may reduce hyperpigmentation.

The exact duration can vary according to vessel pattern and protocol.

I do not think compression should become a punishment imposed for an arbitrary number of weeks.

It is a mechanical adjunct with a specific purpose: supporting treated veins and reducing some of the inflammatory and haemodynamic consequences during early healing.

Walking is usually part of recovery rather than bed rest

Sclerotherapy does not generally require prolonged immobilisation.

Normal walking supports venous circulation and is usually encouraged after treatment unless another medical issue dictates otherwise.

This is particularly relevant because immobility itself is a venous-thrombotic risk factor.

The patient should understand which activities are temporarily restricted and which are useful rather than interpreting a vascular treatment as a reason to stop moving completely.

Sun exposure matters when pigmentation is developing

Bruised and inflamed skin can respond to ultraviolet exposure with more persistent pigmentation.

Photoprotection is therefore sensible while treated superficial veins and injection sites are healing.

A successful vein treatment can still produce an avoidable cosmetic problem if the recovery environment encourages pigment persistence.

The first session rarely needs to erase every vessel

Some veins close immediately and become progressively less visible.

Others require more than one treatment.

Some tiny vessels may become easier to treat only after larger reticular veins have been addressed.

I prefer to allow the vascular response to mature before deciding that every remaining line represents undertreatment.

This also reduces the tendency to exceed reasonable sclerosant exposure simply to create a more dramatic one-session photograph.

New spider veins in the future do not mean the old treatment stopped working

Sclerotherapy closes selected veins.

It does not remove the biological tendency that allowed superficial veins to become visible in the first place.

Genetics, hormones, pregnancy, prolonged standing and underlying venous haemodynamics can contribute to the development of new vessels over time.

A successfully treated vein can remain closed while different vessels appear elsewhere.

Maintenance therefore means assessing new anatomy.

It should not mean routinely reinjecting an old treatment map.

Laser and sclerotherapy should be selected by vessel, not by which technology sounds more modern

Transcutaneous vascular lasers can be particularly useful for very small vessels, facial telangiectasias and patients in whom sclerosant injection is unsuitable.

For larger leg reticular veins and their feeder networks, sclerotherapy is often more efficient.

Current vascular guidelines recognise both approaches rather than declaring one universally superior.

The treatment should follow vessel diameter, depth, colour, location and venous anatomy.

What a good sclerotherapy result means to me

I want the treated vein to disappear or become sufficiently inconspicuous that it no longer dominates the skin.

I also want the surrounding skin preserved.

I do not consider extensive brown staining, ulceration or unnecessary treatment of normal venous anatomy an acceptable price for cosmetic perfection.

And I do not expect the leg to remain permanently free of every small vessel.

Normal venous networks exist.

The objective is to treat abnormal or cosmetically meaningful vessels selectively while respecting the circulation they belong to.

When sclerotherapy makes sense to me

I am most comfortable recommending sclerotherapy for appropriately classified leg telangiectasias, reticular veins and selected superficial varicose tributaries when the venous anatomy and patient risk profile are suitable.

For uncomplicated cosmetic C1 disease, treatment can remain relatively focused.

When symptoms, larger varicosities, swelling, bleeding or other signs suggest a broader venous problem, the assessment should expand before the injection plan does.

I become more cautious with acute venous thromboembolism, significant thrombotic risk, known sclerosant hypersensitivity, serious active systemic illness and situations in which the cosmetic benefit is too small to justify the patient’s individual vascular risk.

Sclerotherapy works by closing veins.

The clinical skill lies in knowing which veins are expendable, which veins are feeding the problem and which veins should be left alone.

Frequently asked questions

What is sclerotherapy?

Sclerotherapy involves injection of a sclerosant into a selected vein to damage its endothelial lining, causing closure and eventual fibrosis of the treated vessel.

What types of veins can be treated?

It is commonly used for spider veins, reticular veins and selected larger superficial venous tributaries. Larger or symptomatic varicose-vein disease may require duplex ultrasound and a broader venous treatment plan.

Do all spider veins require ultrasound before treatment?

No. Current guidelines do not recommend routine duplex scanning for every asymptomatic patient with uncomplicated cosmetic telangiectasias or reticular veins. Symptoms or more advanced venous disease can change that recommendation.

What is the difference between liquid and foam sclerotherapy?

Foam displaces blood and increases contact between the sclerosant and venous wall, which can be useful in larger vessels. Liquid treatment remains well suited to many small superficial veins.

Which drugs are used for sclerotherapy?

Polidocanol and sodium tetradecyl sulfate are among the most widely used modern detergent sclerosants. Concentration is selected according to the vessel and treatment protocol.

Does sclerotherapy hurt?

Patients may feel small needle punctures, burning or cramping during injection. Discomfort varies with sclerosant, concentration, vessel and individual sensitivity.

Why can the treated vein turn brown?

Post-sclerotherapy hyperpigmentation can occur from inflammation and breakdown of trapped blood. It often fades gradually but can persist for months in some patients.

What is telangiectatic matting?

It is the appearance of a fine network of new small red vessels around a treated region. Some cases improve spontaneously and the area should be reassessed before automatically reinjecting it.

Can sclerotherapy cause a blood clot?

Local thrombosis within the treated superficial vein is part of the intended mechanism. Extension into the deep venous system is uncommon but is a recognised complication.

Can foam sclerotherapy cause visual symptoms?

Transient visual disturbances and migraine-aura-like symptoms have been reported, particularly after foam treatment. They are uncommon and usually resolve, but new neurological symptoms should be assessed appropriately.

Can sclerotherapy cause skin necrosis?

Rarely, yes. Extravasation, excessive local exposure, vascular compromise or accidental arterial injection can cause tissue ischemia, ulceration and scarring.

Do I need compression stockings afterwards?

Compression is commonly recommended after liquid microsclerotherapy and can improve clinical response and reduce pigmentation. The duration should be individualised.

How many sessions are needed?

That depends on the number, size and network of veins. I prefer staged treatment with reassessment rather than trying to inject every visible vessel in one session.

Will spider veins come back?

Treated veins can remain closed, but new vessels may develop over time because the underlying genetic, hormonal or venous tendency has not necessarily changed.

Is laser better than sclerotherapy?

Neither is universally better. Laser can be useful for very small vessels and when sclerosant injection is unsuitable, while sclerotherapy is particularly effective for many leg reticular and telangiectatic networks.

When would you recommend no sclerotherapy?

I would avoid or redirect treatment when acute venous thrombosis, critical limb ischemia, severe active systemic illness or known sclerosant hypersensitivity is present, and I would reconsider elective treatment when individual thrombotic or medical risk outweighs the cosmetic benefit.