Systems and methods treat superficial venous malformations, such as spider veins. The systems and methods distribute a reactive agent, e.g., a light-reactive agent such as talaporfin sodium or verteporfin, at or near an inner wall of a vein. The systems and methods activate the reactive agent by applying energy, e.g. non-thermal light energy at a wavelength that activates the reactive agent to cause localized injury to the inner wall of the vein.