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Is Sclerotherapy Safe?


Nearly every day I get asked by my patients and by my medical colleagues, “Is Sclerotherapy Safe?”.

Sclerotherapy has an excellent safety profile. However in common with all highly effective medical treatments, sclerotherapy for leg veins, hand veins and cosmetic veins elsewhere on the body, does have complications and side effects that patients, doctors and nurses should know about. They are classified as Major, Cosmetic and Minor. Let’s cover these in detail.

Sclerotherapy is very safe. A French registry of 12,173 procedures confirmed that sclerotherapy has a very low incidence of major complications. The important proviso is that sclerotherapy is safe for carefully selected patients, when it is performed by a skilled practitioner in an appropriate clinical setting who is able to avoid, mitigate and treat the most serious and common complications. 

Major Complications after Sclerotherapy

Anaphylaxis after Sclerotherapy

One of the most feared complications is anaphylaxis, which can be immediate and potentially life-threatening. It is very rare, sporadic and unpredictable. There is no pre-procedure test or associated risk factor that can reliably identify those patients who may suffer an anaphylactic reaction to a sclerosant. The routine of providing a “test injection” does not protect against a subsequent anaphylactic reaction. With the exception of hypertonic sclerosants, any sclerosant may cause an anaphylactic reaction. 

Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction. This is characterised by rapidly developing life-threatening airway and/or breathing and/or circulation problems usually associated with skin and mucosal changes. A diagnosis of anaphylactic reaction is likely if a patient develops a sudden illness usually within minutes of injection with rapidly progressing skin changes and life-threatening airway and/or breathing and/or circulation problems. The reaction is usually unexpected. 

Anaphylaxis is likely when all of the following 3 criteria are met: 

  • Sudden onset and rapid progression of symptoms 
  • Life-threatening Airway and/or Breathing and/or Circulation problems 
  • Skin and/or mucosal changes (flushing, urticaria, angioedema

The following supports the diagnosis:

  • Exposure to a known allergen for the patient 

Remember: Skin or mucosal changes alone are not a sign of an anaphylactic reaction. Skin and mucosal changes can be subtle or absent in up to 20% of reactions (some patients can have only a decrease in blood pressure, i.e., a Circulation problem). There can also be gastrointestinal symptoms (e.g. vomiting, abdominal pain, incontinence).

Tissue necrosis after Sclerotherapy

Necrosis may occur either locally at the site of injection because of extravasation (accidental injection of the sclerosant around the vein – missing the target) or veno-arteriolar reflex vasospasm or distant to the injection if the sclerosant enters an artery. 

Extravasation of large quantities of sclerosant is a consequence of poor technique. Any sclerosant of any concentration can cause tissue necrosis, usually skin ulceration, if a large volume is injected outside the blood vessel. So, if you notice a bleb, or if the injection is more uncomfortable or “stingy” than expected, you must stop injecting immediately. Even the most skilled and experienced sclerotherapist will cause a bleb on occasions, but the important thing here is to recognise it and stop injecting immediately.

Veno- arteriolar reflex venospasm describes the phenomenon in which arterioles in association with the injected veins develop intense spasm after the injection of sclerosant. The skin turns white and subsequently, skin loss may occur. This blanching of the skin is not to be confused with blanching of the vessels. Successful injection of reticular veins and telangiectasia is indicated by blanching of the vessels but blanching of the skin is a serious warning sign to stop injecting immediately. At all times, the injection site must be carefully watched for intense skin blanching. 

Injection of sclerosant into an artery is a catastrophe which can cause very large areas of tissue loss and may even result in amputation. A system of sclerotherapy that mitigates against this risk must be in place, and policies and procedures for dealing with this complication must be in operation. 

A rare form of tissue necrosis called (also known as Livedoid dermatitis or Embolia Cutis Medicamentosa) may occur after Microsclerotherapy. It is thought to be a chemical vasculitis secondary to sclerosant entering the arteriolar skin circulation. Although it is rare, it may cause extensive and severe skin loss. It is recognised by intense pain on injection and blanching of the skin. 

Venous thromboembolism after Sclerotherapy

Deep vein thrombosis and pulmonary embolism can occur after sclerotherapy. Fortunately, venous thromboembolism is rare, many deep vein thromboses are silent and do not cause problems; but it is a potentially life-threatening complication. Venous thromboembolism may be suspected in patients with leg swelling, pain, shortness of breath or cough.

Neurological Events after Sclerotherapy

The most common neurological events associated with sclerotherapy are visual disturbance and migraine. The clinical presentation of the visual disturbances is similar to the aura of a migraine. All cases spontaneously regress.

There are reports of transient ischaemic attacks and stroke after sclerotherapy, but these complications are extremely rare. 

Nerve Damage after Sclerotherapy

Damage to sensory and motor nerves after sclerotherapy is a rare but recognised complication. Though rare, it seems to be an issue when injecting in the popliteal fossa behind the knee.

 Oedema after Sclerotherapy

Oedema is another rare complication of sclerotherapy and it can occur as a consequence of poor bandaging technique or ill-fitting stockings. It may also occur following extensive Microsclerotherapy causing lymphatic dysfunction.

Cosmetic Complications after Sclerotherapy

What is Matting after Sclerotherapy

Matting-Complication-after-sclerotherapyTelangiectatic matting is the proliferation of small vessels less than 0.2 mm in diameter that may appear after sclerotherapy or surgical treatment of varicose or telangiectatic leg veins. Telangiectatic matting can mar an otherwise good cosmetic result and be a cause for complaint. This complication has an incidence of 10-20%. In most cases the matting fades with time, but in some cases, it can respond to treatment of refluxing feeder veins.

What is Pigmentation or Staining after Sclerotherapy 

The reported short-term incidence of pigmentation ranges from 10% to 30%.  Post-sclerotherapy pigmentation is usually due to a combination of both melanin and haemosiderin pigment deposits. Haemosiderin is derived from extravasated red blood cells. In my opinion, some degree of pigmentation after sclerotherapy occurs in all cases. It may occur as a reaction to the inflammatory process. 

How often does Sclerotherapy Result is Disappointment?

In my opinion, the most frequent complication of sclerotherapy is disappointment, when the result of treatment does not match the patient’s expectations. Fortunately, it can be mitigated by a careful assessment of the patient’s expectations and by providing appropriate information of the anticipated outcome of treatment as part of the consent process. A recent audit of my own practice indicates that around 5% of my patients are disappointed.

Minor Complications

Urticaria after Sclerotherapy

Raised, red and itchy areas at the site of injection are self-limiting and usually do not require treatment.

Skin irritation and bruising after Sclerotherapy

Irritation is normally due to the use of compression stockings and blisters may appear behind the knees where the stockings bunch up. Compression bandages and direct application of compression pads or tapes onto the skin can also result in skin irritation and blistering. Such complications are usually of a self-limiting and transient nature and can be treated with topical agents such as antihistamines or hydrocortisone. 

What is Retained Coagulum After Sclerotherapy?

Sclerotherapy can result in the formation of a ‘coagulum’ identified within the treated vessel. Retention of coagulum is usually associated with tenderness and may predispose to post-treatment pigmentation. Removal of the retained coagulum relieves the tenderness and may help prevent discolouration. 


How to Mitigate and Manage Complications After Sclerotherapy

In principle, risks of complications can be reduced by 

  • Careful patient assessment and selection
  • Duplex Ultrasound Imaging when indicated
  • Thorough understanding of the patient’s expectations
  • A detailed explanation of the sclerotherapy process
  • Before and After Photography
  • Meticulous  Injection technique
  • A consistent approach to post-procedure management
How to Avoid Anaphylaxis After Sclerotherapy

Sclerosants should not be administered if the patient has a known allergy to that sclerosant. I exercise caution and avoid sclerosants in patients with a history of anaphylaxis and who are severely atopic with multiple severe allergies. I am very cautious when treating patients with severe atopic asthma. Since anaphylaxis as a complication of Microsclerotherapy cannot be prevented in all cases, practitioners must be prepared to identify and manage this very rare but potentially fatal complication. I strongly urge you to read the guidance from the resuscitation council and to download the treatment poster for display in your treatment area. It is important that your anaphylaxis kit is checked regularly and that it is readily available.

How to Avoid Thromboembolism after Sclerotherapy

I avoid sclerotherapy in patients who have had a recent or active deep vein thrombosis or pulmonary embolism. All my patients are assessed for the risk of venous thromboembolism in line with NICE Guidance NG89. Where possible, I avoid treating patients with a history of thromboembolic events, those with a thrombophilia and those with active superficial venous thrombosis. I ask the patient to flex and dorsiflex the ankle of the injected limb intermittently during sclerotherapy to disperse the sclerosant. All patients should be encouraged to remain active and keep hydrated. I generally avoid treating patients who are about to take a long-haul flight or who have just come off one.

How to Avoid Central Neurological Events after Sclerotherapy

I avoid sclerotherapy in patients with known symptomatic right to left shunts and I exercise caution in patients who have had previous neurological events with sclerotherapy or who are migraine-sufferers. In particular, the patient should remain lying down for a longer period of time and avoid performing a Valsalva manoeuvre in the early period after the injection. This means that the patient should not help with the application of stockings (if it is your practice to use medical compression after Microsclerotherapy). In my opinion, all patients should remain in the clinic for up to 30 minutes after sclerotherapy to observe for neurological symptoms or minor degrees of wheeze or cough.

With regard to visual disturbance and migraines, many of my patients have benefitted from wearing dark glasses during the sclerotherapy session and some have taken a prophylactic dose of a triptan as prescribed by their own family doctor.

How to Avoid Tissue Necrosis and Ulcers after Sclerotherapy

I inject small volumes of sclerosant, slowly under low injection pressure. If the injection of sclerosant is painful or if a bleb develops, I stop injecting immediately and I vigorously massage the area to disperse the sclerosant. 

I stop injecting immediately if there is blanching of the skin which may indicate veno- arteriolar reflex vasospasm or intense pain. I am always mindful of the risk of intra-arterial injection around the malleoli and in the popliteal fossa. 

Here the principle is not to inject unless the vessels are visible or palpable. If in doubt, do not inject.

The risk of Nicolau Syndrome may be reduced by limiting the volume of sclerosant injected at any one site.

How to Avoid Nerve damage After Sclerotherapy

I rarely use stockings or bandages after Microsclerotherapy, thus reducing the risk of compression neuropraxia. If needed, I ensure patients are carefully measured for stockings and that they fit correctly, If bandages are needed, I ensure that the popliteal area and the anterior subcutaneous border of the tibia are well padded so that stockings and bandages are less likely to compress nerves in these areas. Great care must be taken when injecting areas where nerves are very superficial, namely around the head of the fibula and around the malleoli. 

How to Avoid Oedema After Sclerotherapy

I rarely use stockings or bandages after Microsclerotherapy. If needed, I am very careful when I apply bandages to avoid pinch points on tendons and subcutaneous bony prominences or subcutaneous nerves. I limit the amount of sclerosant in one session in order to limit the inflammatory process around the veins and their accompanying lymphatic vessels.

How to Avoid Telangiectatic Matting After Sclerotherapy

I ensure that I treat proximal reflux first before treating smaller veins such as reticular veins and telangiectasias. In this way I hope to avoid and limit telangiectatic matting. In addition, I inject small volumes of the lowest strength sclerosant under low pressure. 

How to Avoid Pigmentation After Sclerotherapy

Some degree of pigmentation is unavoidable. I mitigate this by using the lowest strength sclerosant. I use topical steroid cream after sclerotherapy as I believe that this practice may reduce the risks of post-inflammatory hyperpigmentation. When treating larger reticular veins, post-procedure compression hosiery may reduce pigmentation if worn for 1-3 weeks.  If clot forms within the vessel, I release it and it is my practice to see patients 2 weeks after Microsclerotherapy.

In cases where pigmentation is more pronounced than expected or in cases where telangiectatic matting occurs, I look for the presence of undiagnosed proximal reflux and I perform a repeat diagnostic ultrasound scan before proceeding with more sclerotherapy. 

How to Avoid Skin irritation After Sclerotherapy

I apply topical steroid cream and I do not use tape.

What about Disappointment After Sclerotherapy?

Careful assessment, careful management of expectations, written information and a well-documented consent process all mitigate against the possibility of disappointment. I photograph patients before and after treatment and this practice is supported by a recent publication which showed that patients are more satisfied with the results of sclerotherapy after being shown before and after photographs 2 months after the procedure. Clinical photography was proven to be a very effective method of improving patient satisfaction.

When discussing the outcomes of treatment, be very careful in your use of language when describing the aims. I strongly suggest that you avoid the use of words such as “cure”, “remove”, “vanish”, “instant” and instead use words such as “improve”, “fade” “temporary” and “gradually”. Over-promising and under-delivering will lead to complaints. In addition, emphasise that sclerotherapy is a process involving several treatments over many weeks or months and that the results may not be fully apparent for as long as a year. During this process, the veins may look worse. Aim to under-promise and over-deliver.

When to refer patients with complications

In all cases of anaphylaxis, the emergency services should be called at the same time that resuscitation is started and adrenaline is given. 

If intense skin blanching develops at the time of injection, or if there is severe pain at the time of injection, an urgent vascular second opinion should be sought by referral to the emergency department of your local hospital. 

Should small areas of skin loss occur, it may be appropriate for you to manage this complication with local dressings and compression, depending on your own clinical experience and competence. 


Sclerotherapy requires dexterity and skill. Good results require constant practice, good technique, a systematic approach to aftercare and good patient information. A team approach is needed to ensure that facilities and appropriately trained staff are available to support the delivery of Sclerotherapy and to treat complications. 

Serious complications are rare and they can be avoided in most cases with the exception of anaphylaxis. All practitioners must be able to identify and treat patients with this potentially life-treating complication. 

The possibility of tissue loss can be mitigated against by only injecting vessels that are easily seen or felt, by avoiding sites close to neurovascular bundles and by being particularly careful in the popliteal fossa. The injection site should be watched carefully during the injection for bleb formation or skin blanching.  These 2 signs or pain on injection indicate the need to stop injecting immediately.

Minor and cosmetic complications are usually self-limiting and get better of their own accord given sufficient time. The patient should be seen regularly during the resolution period to allay anxiety and to demonstrate that you take these complications seriously. Empathy and concern will mitigate against complaints. Disappointment can be avoided and mitigated by a careful explanation of the limitations and expected outcomes of sclerotherapy and by taking clinical photographs before, during and after treatment. With appropriate consent and permission, showing patients the photographs of previously treated patients can also help in the consent process and prepare patients for the sclerotherapy process. Empathy and concern will mitigate against complaints. 

If you are a doctor or nurse and you would like more information about sclerotherapy

If you are a patient and you would like more information about sclerotherapy 

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Dr Haroun Gajraj

Dr Haroun Gajraj

The VeinCare Centre | Dorset | We help people find freedom from unsightly veins, veins causing pain, ache and throbbing as well as veins causing serious medical complications such as phlebitis, varicose eczema and leg ulcers.

We can help you. Please call 01935 873951 for more information

The VeinCare Centre

We help people find freedom from unsightly veins, veins causing pain, ache and throbbing as well as veins causing serious medical complications such as phlebitis, varicose eczema and leg ulcers

Call 01935 873951

Please call us to make an enquiry or send us a message using our contact form


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