The most common side effect is skin colour change, along the treated vein. The discolouration may take 6 to 12 months to disappear.
Itching, bruising, pain, and blistering may occur where the veins were treated.
Scarring may happen, if ulcers or skin/fat necrosis forms around the treated vein. This would happen if sclerosant is injected outside a vein, or sclerosant escapes through the wall of a weakened vein.
A mild or severe (anaphylactic) reaction to the sclerosant. (Severe reaction is very rare.)
Blood clots or damage in the deep vein system.
Failure of treatment to prevent varicose veins from returning.