What Causes Body Rashes In An Year Old Child?

my 20 month old daughter is constantly gettint these rashes all over her body but only in one area at a time it looks like someone took a rubberband and snapped her in the cheek with it leaving a welt but this has been going on for a few months now it does not seem to bother her no fever no itching she acts like its not even there and today its by her eye