Venous flares (also known as “spider veins” or “thread veins) are small blue or purple visible veins in the skin usually on the legs, though they can occur elsewhere. They often occur in people who also have varicose veins but sometimes they occur on their own. Venous flares are not a serious condition and do not carry any long term risk of complications such as DVT (clots) or leg ulcers. No treatment is required to prevent complications but some people find them unsightly and would like to have them treated. As with varicose veins, compression stockings may help compress the veins and may prevent new flares for forming but they will have no effect on existing flares.


For those who would prefer treatment for their flares, there are a number of different treatments available. These include injection sclerotherapy, visible light (photodynamic) therapy, and laser therapy. Only injection sclerotherapy is available in our clinic.


You will be assessed in OPD and your medical history taken including whether you have any other chronic medical conditions and whether you take any regular medications. Your legs will be examined. Occasionally, specialised tests will be ordered but most patients with venous flares do not require any further investigation.

If varicose veins are present and it is intended to treat those, it is usually advisable to treat the varicose veins before treating the venous flares. One reason for this is that bruising often occurs as part of the surgical treatment for varicose veins may cause bruising and bruising may trigger the formation of new venous flares.

Injection sclerotherapy

Injection sclerotherapy is performed in the day ward. The procedure is usually performed on an outpatient ambulatory basis and no anaesthetic is required. You do not need to fast before the procedure. You should wear clothing that is loose and easy to remove. You do not need anyone to bring you to the clinic and you can drive home after treatment or go to work afterwards.

Before your treatment you will be measured for a compression stocking.

Treatment usually takes 10-15 minutes and is painless or associated with mild discomfort. An irritant solution (ScleroveinTM) is injected directly into the vein using a very small needle. This irritant displaces the blood in the flare and causes irritation of the lining of the tiny veins in the flare. This cases the walls of the tiny veins to stick together obliterating the flare.

Multiple sites can be treated at one sitting but there is a limit to total volume of sclerovein that can be used at any one time and it you may require several visits before your treatment is complete. Repeat treatment sessions will be booked before you leave the clinic

At the completion of each treatment small dressings or Band-aids are applied to the puncture sites. These can be left in place for up to 5 days but they need not be replaced if they fall off before that time.

To help the flare vein walls stick together, a compression stocking will be applied after the procedure and you should wear this for 5 days (day and night). The skin around the injection site may be itchy, tender or sensitive to heat and it not recommended to take a hot bath or shower for 5 days. However, you may remove the stocking for washing and reapply it afterwards.

Over the first few days or weeks, you may notice some discomfort, reddening, or tenderness of the skin. You can take simple painkillers (paracetemol) but if there is extensive redness, swelling or pain, you should check with your GP or contact the vascular clinical team for further advice.


Complications are uncommon (experienced by approximately 1% of patients) and the most frequent is a brown discolouration (pigmentation) of the skin resulting from the escape of some blood from the vein into the skin at the time of injection. This will usually fade over time but can last a year or more. In some cases, this pigmentation will be permanent.

Rarely, an ulcer of the skin may occur where the sclerosant damages the skin. This can leave a wound that is slow to heal and, even when it does heal, there may be a permanent mark or scar. If this happen, you may need treatment with compression bandages for weeks.

In addition, the sclerotherapy may be ineffective – your flares may be resistant to treatment,. Occasionally, the dark blue or purple falesr may be replaced by tiny red flares. While these are less visible than the blue/purple flares, they are still visible and some peopl are bothered by these. These do not respond well to injection sclerotherapy treatment.

Deep vein thrombosis or a clot could occur after sclerotherapy treatment but the risk of this happening is very low.

Finally, the treatment only addresses the visible flares and does not prevent more flares for forming over time. The sclerotherapy treatment can be repeated in the future if necessary.