For about 15 years I have had occasional bumps appear on the soles of my feet. They are small, filled with clear to green fluid and occasionally itch. I pop them with a needle when they appear. They either dissappear thereafter or refill up with fluid. I have recently had the worse flare up after spending a week in Hawaii wearing straw type sandals. Although I wear sandals the majority of the time I was wondering if my shoe preference might be the cause. Do you know what this is, what causes it and how I might prevent it?