Side effects of “injections” – sclerotherapy

What are “injections” that are given in the veins?

While the video shows you how it looks, there are several questions, which I get asked mainly related to the complications, and which I thought we should discuss.

These “injections” are also known as “sclerotherapy.” These can be done for the very fine veins – “reticular veins / spider veins” or the larger veins “ varicose veins”. The smaller ones (reticular veins) are treated simply with using the medication only.

On the other hand, the larger “varicose veins” are often treated with “foam”. Foam is a mixture of the medication used for sclerotherapy with either air or carbon dioxide.

“Foam sclerotherapy” is more effective than the medication itself and allows lower dosage of the medication to be used.

Put simply, the “injections” or sclerotherapy medications are a form of medical detergent (polidocanol) or concentrated salt solutions (hypertonic saline). The side effects of the “medicine” used for the injections can be allergic reaction to the medication, skin blisters, breakdown of the skin (ulcer).

All of these are treatable and quite rare. Let’s talk about each of them and what would you experience.

Allergic reactions. Frankly these are exceedingly rare. So much so that in the thousands of injection we have done, we have yet to see one. If however it does happen, treatment depends upon the severity of the reaction. This is why, one needs to do the injections in a facility where there are “anaphylactic kits” in place to manage these.

Skin blisters. These can happen when either the medication leaks out of the blood vessel, to reach under the skin or from the tape which some of us are sensitive to. Once again, these simply require skin care to resolve them, which should happen within a week or two.

Skin ulcers. These can happen several reasons, from a skin blister becoming more severe or from the medication inadvertently being injected into a small artery as opposed to a vein. Often times the smallest arteries are indistinguishable from the veins. But by design, the arteries are deeper and are very rarely injected. There are other distinguishing features of blood in the arteries, which also prevents inadvertent injection into the arteries.

Some of these veins can become painful and red after the injections, both after foam and simple sclerotherapy. Rarely, “matting” or development of new network of veins around the previously injected veins may develop.

These were the side effects of the medicine used for the injections.

Now let’s talk about “foam”. This is the milky white mixture, which is injected into veins – typically the larger ones. As mentioned, it allows more veins to be treated at a smaller dose.

The foam is a mixture of a gas with the medication. The typical mixture is in a ratio of 1 part of medication to 4 parts of gas. The key in this is the “gas” Typically, we use at most 15 ml of foam at each session. The reason being, the risk of side effects. Let’s talk about these….


Metallic / medicinal taste


Dry cough

Tingling around the mouth

Visual disturbances – typically stars and floaters

Development of blood clots (DVT) in some of the deep veins in the lower leg

Perhaps, most important is that sometimes chest tightness can develop with some breathing difficulty.

We must keep in mind that there are other more common side effects such as pain, bruising, and recurrence of veins.

All of these are typically transient and not life threatening. Perhaps most importantly, the risk of any of these is exceedingly low when less than 20 ml of the foam is used ( 10 ml & 2 syringes ). Furthermore, the chance is lowered even more with the use of carbon dioxide as opposed to air.

Disclaimer: These are commonly asked questions by patients and meant for patient education. They are not an alternative to a direct conversation with your treating physician.