The early signs of chicken pox are very quick to develop once the rash is there. It usually starts with just one or two spots on the trunk and back, after which it rapidly starts to spread, potentially affecting every part of the body, sometimes within just a few hours. These spots turn into fluid filled blisters that eventually dry up and crust over. Once all the spots have blistered and all the blisters have dried up, the patient is no longer contagious.