Never had this problem before. On the ball of my right foot, i.e. the bottom of the foot, there started to appear blister size pimples filled with a watery pus. If I pierce the skin, the water would drain out, and after removing the loose skin, a scab would form, which I thought fixed the problem. But then another pimple would appear in a slightly different location, which I pierce, a scab forms. And another pimple appears...Doesn't hurt at all. Anyone ever have this problem, and what causes it? I don't think it's caused by rubbing like getting blisters on the hand, and it happens even when I'm wearing just regular street shoes for the past 3 - 4 days without having played any tennis. Any ideas? Or should I go see a foot doctor?