Compare · Sclerotherapy types
Foam vs Liquid Sclerotherapy: Which Is Used When?
Quick answer: Liquid sclerotherapy injects the medicine as a fluid and is well suited to tiny spider veins. Foam sclerotherapy mixes the same type of medicine with air into a microfoam that pushes blood aside, so it works better in larger or hidden veins and shows clearly on ultrasound. At LEDAS in Busan, the doctor chooses between them for each vein after an ultrasound scan.
Key facts at a glance
- Same family of medicines: foam is made from a liquid sclerosant mixed with air or gas.
- Liquid: mixes with blood and is diluted; best for small, superficial vessels.
- Foam: displaces blood, keeps full contact with the vein wall; suits larger and deeper veins.
- Visibility: foam is easy to see on ultrasound; liquid is not.
- Foam-specific effects: brief chest heaviness, dry cough or visual flicker in some people.
- At LEDAS: foam used in ultrasound-guided treatment (DGS/UGFS) and for hand veins; liquid or foam in surface sclerotherapy (SCT).
What is the difference between foam and liquid sclerotherapy?
Both forms of sclerotherapy close veins by injecting a sclerosant, a medicine that damages the inner lining of the vein so its walls stick together. The vein then closes and is gradually absorbed. The difference lies in the physical form of the medicine.
Liquid
In liquid sclerotherapy, the sclerosant is injected as is. Inside a vein it mixes with blood, which dilutes it and carries it away. In very small vessels such as spider veins , this is fine: the volume of blood is tiny, and a gentle, diluted effect is exactly what is wanted.
Foam
In foam sclerotherapy, the sclerosant is mixed rapidly with air (or a gas) to form a fine, stable foam. Foam behaves like a plug: it pushes blood out of the way and keeps the medicine in direct contact with the vein wall at full strength. That makes it more effective in larger veins for the same or smaller dose of medicine. Foam also shows up brightly on ultrasound, so the doctor can watch exactly where it goes. Learn more on our foam sclerotherapy page.
When is liquid sclerotherapy used?
- Fine red or purple spider veins (telangiectasia).
- Very small reticular veins close to the skin.
- Delicate areas where a gentle effect is preferred.
- Touch-up sessions for small residual vessels.
When is foam sclerotherapy used?
- Larger reticular veins and branch varicose veins.
- Hidden refluxing branches and perforator veins, treated under ultrasound ( duplex-guided sclerotherapy ).
- Tangled recurrent veins after previous surgery.
- Prominent hand veins, using a carefully reduced concentration (see hand vein treatment ).
- Some patients who are not suited to thermal treatment.
Are the side effects different?
Many side effects are shared: bruising, firm and darker treated veins during healing, brownish skin staining that fades slowly, and occasionally a blush of fine new vessels (matting).
Foam has some additional, usually short-lived effects. Because tiny amounts can travel in the bloodstream, some people notice a brief feeling of chest heaviness, a dry cough, or a visual disturbance such as flickering lights shortly after injection. These generally settle on their own. Rarely, more significant reactions can occur, so tell your doctor if you have a history of migraine with aura, a known hole in the heart, previous blood clots or allergies. Using ultrasound guidance, the smallest effective volume and walking afterward helps limit these effects. See side effects and risks .
Call emergency services for sudden breathlessness, chest pain, or weakness, numbness or speech difficulty after any injection treatment.
How does LEDAS decide which to use?
- Every leg is first scanned with Philips EPIQ Elite ultrasound to find any underlying reflux.
- Large straight trunks are closed with EVLT .
- Hidden branches and perforators are treated with ultrasound-guided foam.
- Visible surface veins are treated with liquid or foam depending on their size.
Doses and concentrations are adjusted for each vein. You do not need to choose; the doctor will explain why a particular form is used for each area.
Foam vs liquid sclerotherapy side by side
| Liquid sclerotherapy | Foam sclerotherapy | |
|---|---|---|
| Form | Fluid | Microfoam (sclerosant + air or gas) |
| Behavior in the vein | Mixes with blood, diluted | Displaces blood, full wall contact |
| Best for | Spider veins, tiny reticular veins | Larger reticular, branch, perforator and recurrent veins |
| Ultrasound visibility | Poor | Excellent |
| Typical guidance | Direct vision | Ultrasound for deeper veins |
| Extra transient effects | Rare | Possible brief chest heaviness, cough, visual flicker |
Foam vs liquid sclerotherapy – frequently asked questions
Is foam sclerotherapy stronger than liquid?
Foam is more effective per dose in larger veins because it stays in contact with the vein wall rather than mixing with blood. That does not make it better for everything: for tiny spider veins, liquid is often preferred because a gentle effect is enough and causes less irritation.
Can foam and liquid be used in the same session?
Yes. It is common to use foam for larger or deeper veins and liquid for fine surface vessels during the same visit. The doctor chooses the form and concentration for each vein based on its size, depth and the ultrasound findings.
Why does foam sclerotherapy need ultrasound?
Foam is often used in veins you cannot see from the surface. Ultrasound lets the doctor place the needle inside the right vein, watch the foam spread and keep it out of the deep veins. Foam is highly visible on ultrasound, which makes this precise guidance possible.
Does foam or liquid need more sessions?
It depends on the veins, not just the form of medicine. Spider veins often need more than one liquid session. Larger veins treated with foam may also need repeat injections. LEDAS re-examines after treatment to plan any further sessions.
About this page
Clinical information:
LEDAS Varicose Vein Clinic, led by
Dr. Kim Byoung Joon , thoracic and cardiovascular surgeon, founding member of the Korean Society for Phlebology.
Medical reviewer:
Dr. Kim Byoung Joon ·
Review status:
Pending ·
Last updated:
October 2026
This page is general information and not a diagnosis. Treatment is decided only after an in-person examination. Read our
editorial policy .
Related: Foam sclerotherapy · Sclerotherapy · Sclerotherapy vs laser · Duplex-guided sclerotherapy · How many sessions?
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