In What Cases is There a Risk of Scarring from Sclerotherapy?

Following the acute setting where a patient can have an allergic reaction (rare), bruising (common) which will resorb and fade, phlebitis and deep vein thrombosis (are rare), the likelihood of hyperpigmentation is real and warrants the use of compression stockings for a period of 2 weeks to 3 months. 

Sclerotherapy,in general, has very few side effects and associated risks.  Both of these decrease as the experience of the injector increases.  The more common side effects include itching, redness, bruising, discoloration of the injected veins and hematoma formation.  Although "more common" they are not frequent.  The less common side effects would be staining, allergy and the possibility of DVT.   Even less common is the risk of stroke which can occur with the foamed solutions. Having stated all of this, it has been my experience over 20 years of injecting veins that the risks and complications are very few and far between and sclerotherapy is an extremely safe procedure when done by experienced hands.

Scarring can occur if the sclerosant is injected into the skin surrounding the vessel. If blood becomes trapped in areas treated darkening of the skin can occur.