Whenever my five month old Coton has to encounter people she has a surge of adrenaline and needs to eliminate, but often is huddled up away from the person and hence dirties herself.
She even does this at obedience class when she is approached or handled by others. She will tolerate the other dogs, not matter how big, noisey they may be, but if someone approaches she'll back away and hide. If she is handed to them then a brown pressie will soon follow.
She seemed to display this from an early age, and seems to have got worse these past few months.