I am suffering with a problem since 5 years. I was unable to control it, feeling much painful there where it was blistered in between the buttocks top most area. It use to form like a small balloon & slowly it gets increased & bursts on some day, then it will be very hard for me, blood & pus will be bleeding at big amount. it continues for 3 to 4 days & then it forms like a new layer on that skin. it will be dropped automatically. It repeats again & again.