Scle­rother­a­py is a med­ical pro­ce­dure used to elim­i­nate vari­cose veins and spi­der veins. It involves an injec­tion of a solu­tion direct­ly into the vein. The solu­tion irri­tates the lin­ing of the blood ves­sel, caus­ing it to swell and stick togeth­er, and the blood to clot. Over time, the ves­sel turns into scar tis­sue that fades from view.