What Causes Recurrent Water Blisters On Different Body Parts?

my dad who is bed ridden has recurrant water blisters that form on different parts of his body..usually lasting about a week or so, filled with clear fluid, about the size of a half of golf ball. No itching..they come, drain on their own reappear a couple of times than are gone for good. Ocassionally he gets small ones about the size of a eraser that form in the morning but are gone by the afternoon.. any ideas