Clear Fluid In Menstruation What Causes Blisters With Clear Fluid On Hands/feet?

What causes blisters with clear fluid on hands/feet? - clear fluid in menstruation

Discovered my younger sister, the small blisters on the soles. They are very small, small size vesicles filled with clear fluid. They went on their feet, but back then. Now they appear on the palms and fingers. She says it burns really bad, and if new, more stretching. Suggestions on what could be? She tried cortisone creams / lotions, but that does not help.