What cause your foreskin to completely close up?

Never completely: If a foreskin closed up completely, one would not be able to pee. If it closed up almost completely, it would balloon up each time he urinates. Infection or a skin disorder can cause foreskin problems... but we would hope that one's foreskin has been loose and easily able to pull over the glans, rinsed off daily, and kept in good condition all the time since late childhood.