Published by CURA Vein Doctors · Updated September 2026 · Sourced from peer-reviewed vascular literature
Sclerotherapy has been used to treat veins since the 1930s and remains one of the safest procedures in vein medicine, but safe doesn’t mean risk-free. Here’s an honest breakdown of what can actually go wrong, and how often it really happens.
Is Sclerotherapy Safe?
Sclerotherapy is considered one of the safest vein procedures available, with serious complications occurring in well under 1% of cases according to large-scale data. Minor, temporary side effects like bruising, redness, or mild discomfort are common and expected, while dangerous complications like blood clots or allergic reactions are rare. Treated veins also commonly look darker and firmer for a few weeks before fading; this is the vein turning into scar tissue your body is breaking down, not a sign something’s wrong.
What Are the Risks of Sclerotherapy?
| Side Effect | How Common |
|---|---|
| Bruising or soreness at injection sites | Very common, expected in most patients |
| Temporary skin darkening (hyperpigmentation) | Common, usually fades within months |
| Small new red vessels (matting) | Occasional, sometimes fades on its own |
| Superficial phlebitis (vein inflammation) | Uncommon |
| Allergic reaction to the solution | Rare |
| Deep vein thrombosis (DVT) | Rare, under 1% in large studies |
| Skin necrosis or nerve injury | Very rare, typically tied to injection technique |
How Common Are Blood Clots with Sclerotherapy?
In a large analysis of over 3,700 sclerotherapy procedures tracked through UK hospital records, the rate of venous thromboembolism was just 0.19%, notably lower than the rate seen after laser ablation or combined procedures. Smaller studies looking specifically at foam sclerotherapy for larger veins report a wider range, generally between 0.2% and 2%.
How would you know if it happened to you? Watch for throbbing or cramping pain, warmth over the area, swelling that spreads beyond the injection site, redness, or a feeling of tightness in the leg. Any of these after sclerotherapy is worth a same-day call to your vein specialist rather than waiting to see if it passes.
Sclerotherapy for Varicose Veins vs Spider Veins: Does the Risk Differ?
Risk isn’t identical across all sclerotherapy. Treating small spider veins carries a lower complication profile than treating larger varicose veins, which sometimes requires foam sclerotherapy and larger volumes of solution. Foam sclerotherapy for varicose veins has a slightly higher reported rate of DVT and rare systemic effects like temporary visual disturbances or headache, though these remain uncommon overall.
Can Sclerotherapy Be Done Wrong?
Yes, and this is where provider experience actually matters more than the procedure itself. Injecting the wrong concentration of solution, missing the vein entirely, or accidentally hitting a nearby artery instead of a vein can cause serious complications like skin necrosis or tissue damage. These outcomes are rare specifically because they’re almost always tied to technique, not the treatment itself, which is why an experienced, board-certified vein specialist performing the injection under proper guidance is the biggest safety factor you actually control.
When Is Sclerotherapy Not Recommended?
- Pregnancy or breastfeeding
- A history of blood clotting disorders
- Known allergy to the sclerosing solution
- Active infection in the treatment area
- Poor mobility or inability to wear compression afterward
Is It Worth Getting Sclerotherapy?
For most people bothered by spider or small varicose veins, yes. The procedure is quick, complication rates are low, and most patients see visible fading within three to six weeks. Weighed against the alternative, living with veins that won’t improve on their own, most people who qualify find the low risk worth the results.
When Should You See a Doctor of Veins About Sclerotherapy?
See a doctor of veins for an evaluation before scheduling sclerotherapy, since candidacy depends on your specific veins and health history, not a one-size-fits-all checklist. For a full walkthrough of the procedure itself, see our guide on how sclerotherapy for spider veins works.
Frequently Asked Questions
What are the risks of sclerotherapy?
Bruising, temporary skin darkening, and mild soreness are common. Serious risks like blood clots or allergic reactions occur in well under 1% of cases.
Is it worth getting sclerotherapy?
For most people with spider or small varicose veins, yes. Low complication rates and quick, visible results make it worthwhile for those who qualify.
When is sclerotherapy not recommended?
It’s generally avoided during pregnancy, with clotting disorders, known allergies to the solution, or active infection at the treatment site.
How common are blood clots with sclerotherapy?
Large studies put the rate around 0.19% to 2%, depending on vein size and technique, with standard sclerotherapy on the lower end of that range.
Weighing whether sclerotherapy is right for your veins? Call CURA Vein Doctors at +1 973-363-2029 or use the contact page to schedule an evaluation.
References
- The Incidence of Post-Operative Venous Thromboembolism in Patients Undergoing Varicose Vein Surgery Recorded in Hospital Episode Statistics. National Library of Medicine. ncbi.nlm.nih.gov/pmc/articles/PMC3954242
- Sclerotherapy in the Management of Varicose Veins and Its Dermatological Complications. Indian Journal of Dermatology, Venereology and Leprology. ijdvl.com
