Vein Ablation is a medical process used to treat varicose veins off of heat or laser. Although it’s usually safe, sometimes complications can occur. For example, some people may have nerve damage, which can lead to tingling or numbness in the leg. Others may develop blood clots, which can be dangerous when reaching the lungs. Where treatment was performed, there is also a slight possibility of infection, burning or injury. In rare cases, the treated vein can re-open, which can make the problem come back.