What Is That Stuff They Inject Into Veins? Understanding Sclerotherapy and How It Works
What Is Sclerotherapy?
If you’ve ever seen a doctor inject a clear or white solution into visible veins and wondered, “What's inside that injection?” — you’re not alone. The procedure is called sclerotherapy, and it’s one of the most common and effective treatments for spider veins and small varicose veins.
Sclerotherapy is a minimally invasive procedure where a special solution is injected directly into damaged veins. The solution irritates the inner lining of the vein, causing it to collapse, seal shut, and eventually fade away as the body reabsorbs it. Blood is naturally rerouted through nearby healthy veins, restoring smoother circulation and appearance.
What’s in the Injection?
The injected liquid is called a sclerosant — a safe, medical-grade solution designed to gently close unwanted veins.
The most common sclerosants include:
- Polidocanol: A mild, FDA-approved detergent-type solution that causes minimal discomfort.
- Sodium Tetradecyl Sulfate (STS): Another FDA-approved sclerosant that’s slightly stronger and often used for larger veins.
- Hypertonic Saline: A salt-water solution sometimes used for tiny spider veins.
Each solution has the same goal: to irritate and close damaged veins so the body can redirect blood flow naturally.
These agents are carefully chosen based on vein size, location, and patient sensitivity — all under the supervision of a trained vein specialist.
How Sclerotherapy Works Step-by-Step
- Preparation: The skin is cleaned and a fine needle is used to inject the sclerosant directly into the targeted veins.
- Reaction: The vein’s inner wall reacts to the solution and collapses.
- Closure: Over the next few weeks, the vein seals shut and is gradually reabsorbed by the body.
- Circulation Reroutes: Blood flows through healthier veins instead, improving circulation and appearance.
Most sessions take about 30 minutes or less. Patients can return to normal activities the same day, though compression stockings are recommended afterward to support healing.
Does It Hurt? What to Expect During Treatment
Most patients describe the sensation as a mild pinch, tingling, or slight cramp that fades within seconds.
After the procedure, you might notice:
- Temporary redness or bruising at the injection site
- Slight itching or firmness along the treated vein
These effects are normal and typically resolve within a few days.
You’ll be encouraged to walk for 10–15 minutes right after the procedure to promote healthy blood flow and prevent clotting.
Are Sclerotherapy Injections Safe?
Yes — when performed by a qualified vein specialist, sclerotherapy is very safe and effective.
Modern sclerosants like polidocanol are FDA-approved and formulated for comfort. Serious side effects are rare.
Mild reactions such as redness or darkened skin patches can occur but usually fade. Avoiding sun exposure and wearing compression stockings can help your skin heal faster.
How Many Treatments Do I Need?
The number of sessions depends on the size, number, and location of your veins.
- Small spider veins may disappear after 1–2 sessions.
- Larger varicose veins may require 3 or more sessions spaced several weeks apart.
Your provider will develop a personalized treatment plan based on your vein condition and goals.
Results and Recovery
Most patients begin to see results in 3–6 weeks for small veins and up to 3 months for larger ones.
Treated veins fade gradually and do not return — though new veins may form over time due to genetics or lifestyle factors.
There’s no downtime after sclerotherapy. You can resume normal activities immediately, though it’s best to avoid high-impact workouts and hot baths for a few days.
Why Choose BASS Vein Center for Sclerotherapy
At BASS Vein Center, our experienced vascular specialists provide advanced sclerotherapy using the latest techniques for comfort and precision.
We customize every treatment to match vein size, location, and patient goals — all performed in a calm, outpatient environment.
With 7 convenient Northern California locations and more than 24,000 procedures performed, we are the region’s trusted resource for vein health and minimally invasive treatments.
Schedule a consultation today to see if sclerotherapy is right for you and take the first step toward clearer, healthier-looking legs.
Frequently Asked Questions
1. What solution do they inject during sclerotherapy?
A sclerosant solution such as polidocanol, sodium tetradecyl sulfate, or hypertonic saline is injected into the vein. It irritates the vein lining, causing it to close and fade.
2. How soon will I see results after sclerotherapy?
Most patients notice visible improvement within a few weeks. Final results are typically seen within three months.
3. Can veins come back after sclerotherapy?
Treated veins don’t return, but new veins can form over time. Maintaining healthy circulation and wearing compression when needed can help prevent recurrence.
