Sclerotherapy has been used to treat spider and varicose veins for decades, but exactly what happens during a session—and why it works—remains genuinely unclear to most people considering it for the first time. Understanding the mechanism makes the whole process considerably less intimidating and helps set realistic expectations for what a single session can and can’t achieve.
What’s Actually Being Injected
Sclerotherapy involves injecting a sclerosing solution directly into the affected vein, most commonly a saline-based or detergent-based solution depending on vein size and the specific product used. The solution irritates the vein’s inner lining deliberately, causing it to swell, stick together, and eventually scar shut. Blood flow reroutes naturally to healthier nearby veins, and the treated vein is gradually broken down and reabsorbed by the body over the following weeks.
The Session Itself
Most sessions are genuinely quick—often fifteen to thirty minutes depending on how many veins are being treated. The practitioner cleans the area, may use a fine needle for smaller spider veins or ultrasound guidance for larger, deeper varicose veins, and injects the solution directly into the vein. Most patients describe a brief stinging or cramping sensation during injection rather than significant pain, and no anesthesia is typically required for standard spider vein treatment.
What Happens in the Days and Weeks After
Immediately after treatment, mild bruising, swelling, and redness at injection sites are common and expected, generally resolving within one to two weeks. Compression stockings are frequently recommended for several days to weeks afterward, particularly for larger veins, since compression genuinely improves outcomes by helping the vein close properly and reducing the risk of the treated area darkening temporarily before fading. Treated veins don’t disappear instantly—visible fading typically takes three to six weeks for spider veins and can take several months for larger varicose veins, with some residual discoloration lasting longer in a minority of cases.
Why Multiple Sessions Are Often Needed
A single vein may need more than one injection session to fully close, and most patients being treated for a broader network of spider veins require multiple sessions spaced four to six weeks apart to treat the full area effectively. This isn’t a sign the first session failed — it reflects how the treatment is designed to work, targeting veins gradually rather than attempting to treat an entire network in one sitting.
What Sclerotherapy Doesn’t Do
Sclerotherapy treats existing visible veins; it doesn’t prevent new ones from forming, since new spider or varicose veins often reflect an ongoing underlying tendency toward vein weakness (often hereditary) rather than a one-off problem. Patients with an underlying predisposition should expect the possibility of new veins appearing over time, unrelated to whether the original treatment was successful. It’s also generally not the right treatment for larger varicose veins with significant underlying valve dysfunction, where other vascular treatments or referral to a vascular specialist may be more appropriate—a proper assessment beforehand should identify which category a given case falls into.
When Laser Treatment Is Used Instead
Sclerotherapy isn’t the only option for visible veins, and for certain presentations, laser treatment is genuinely the better first choice. Dual-wavelength laser platforms such as ADVATx are specifically cleared to treat spider veins and other vascular concerns on the face and legs, using a wavelength selectively absorbed by the blood in the vessel rather than requiring an injection at all. This makes laser treatment particularly well suited to very fine facial telangiectasia, where injecting each individual thread vein would be impractical, and to patients who would prefer a needle-free option for smaller vessels. For larger varicose veins with a genuine underlying valve problem, sclerotherapy or referral to a vascular specialist typically remains the more appropriate route — the two approaches are complementary rather than interchangeable, and a proper assessment should determine which vessels suit which technology.
The Takeaway
Sclerotherapy works through a fairly straightforward mechanism—deliberately irritating a vein until the body closes and reabsorbs it—but success depends on realistic timelines, appropriate compression aftercare, and often more than one session. Understanding what’s actually happening during and after treatment makes the process far less mysterious, and considerably easier to plan around than going in without knowing what to expect.
If you’d like to explore further, treatments like hair loss treatment, PRP therapy, anti-ageing injection, beauty treatment, body treatment and skin of colour are also worth discussing with your practitioner.
This article is for general information only and doesn’t replace individual medical advice. Suitability for sclerotherapy should be assessed by a qualified practitioner, particularly for larger varicose veins.
