I began noticing these blisters around 22 years old. They have become more numerous over time, I have also discovered that they may be related early testicular trauma. I have popped a few myself, and also got a hard white plaque piece from some of them. It just seems like most of them resurfaced. My Doctor saw them and said: oh those blisters aren't anything! That was the last I heard of it.  I am considering the Dry Ice. I have noticed that overtime they tend to harden them self and fall off. word of warning they will bleed and you wont realize that you are bleeding.