Sclerotherapy is an effective treatment for spider veins, the small red blood vessels usually found on the legs near the skin surface, branching out from larger veins. 
Spider and varicose veins can cause embarrassment, especially when wearing shorts and bathing suits. But these reddish-purple lines on your legs are not unhealthy. The veins are not “broken” but are actually dilated, and they can be obliterated with the injection of a sclerosing solution. This procedure is known as sclerotherapy.
There are several different sclerosing solutions available including saline (salt water) and aethoxysclerol which are among the safest and most popular. Saline is the most popular because it is impossible to have a life-threatening allergic reaction to this solution.
It’s interesting to note that spider veins are not needed for your circulation. They are actually unnecessary detours that can safely be destroyed. Depending on its size, the blood vessel may need to be injected more than once (usually one month between treatments). Numerous vessels can be treated in one session. Note that in general, spider vein treatment is not covered by insurance.
What causes spider veins to form?
Spider veins tend to run in families, and being overweight and child bearing tend to worsen the condition. They are more common in women and become more numerous with age.
The reason these veins stretch is not known, but trauma to an area can lead to their formation. There is no reliable means of prevention.
How does sclerotherapy work?
As we mentioned, spider veins are harmless, so the only reason for treatment is strictly cosmetic. Sclerotherapy is one of the most successful therapies available for removing them.
Sclerotherapy involves injecting a solution through a very tiny needle into the veins. This causes irritation and inflammation inside the vessel and leads to closure of the vessel. With no blood flowing, the veins become invisible and are replaced by scar tissue. The veins fade in 2 to 3 weeks.
The treatment of spider veins does not prevent new ones from forming. It often takes several sessions to treat all of the veins (usually 3 to 5 sessions). Your dermatologist will inject most of the veins in one or two sessions, but only one third to one half of the injected veins actually disappear each session. Usually three sessions are needed to get things started.
After these first few sessions, you will require further sessions every 6 to 12 months to treat the new spider veins which form, depending on how quickly you develop new ones.
Laser therapy can be used to treat the very tiny thread-like veins that may remain after sclerotherapy. This procedure can be the first treatment if your veins are very small.
If you have large varicose veins and spider veins, it is necessary to treat the varicose ones first; this sometimes requires surgery. If there are large veins or extensive varicose veins, you may need an evaluation by a vascular surgeon.
Are there any side effects?
The procedure can be slightly painful for less than one minute. As the saline is injected, it will usually sting or burn briefly and you may feel muscle cramps. The discomfort goes away almost immediately.
After the vein is injected, it will turn red and will be swollen and tender for a few days. It may take several weeks for the redness to completely fade. Bruising will also occur. It will take up to one month for the bruises to disappear. In short, the treated areas will look worse before they look better.
A small ulcer may form when the vein is injected with the saline. The ulcer will heal within several weeks, but may leave a permanent small white scar.
Rarely, brown discoloration can occur over the veins which have been injected. This can look worse than the original veins. This discoloration usually fades over 6 months, but can be permanent. If this complication develops, bleaching cream can be used to speed up the fading process.
Rarely, the treatment can cause many small spider veins to form where a larger one was treated. This is permanent and can look worse than the original problem.
Some precautions to be aware of
You should drink no alcohol (beer, wine, other) nor take any aspirin or aspirin containing medication for one week prior to the treatment session. These drugs make the blood thin and will decrease the effectiveness of the treatment. In general, Tylenol is the only pain medication that should be taken during the week preceding the treatment.
After treatment you may resume normal walking and most activities. Avoid high impact activity (such as aerobics) for at least 3-4 days after sclerotherapy.