Spider leg veins are the small blue veins that can develop on the lower legs ankles and thighs thread veins tend to be less than 1 2mm in diameter compared to varicose veins that are larger and require more specialised treatment microsclerotherapy is the 39gold standard39 for treatment of spider veins and is highly successful treatment involves tiny injections of an irritating chemical into the superficial veins the treated areas typically shrink or completely disappear within the