Contrary to popular belief, poison oak rash does not spread on its own. The rash may appear to spread for two reasons:
Different areas of your body may have come into contact with the urushiol oil at different times, causing the rash to appear in stages.
Areas with thinner skin (like your face) may react more quickly than areas with thicker skin (like your hands).
The fluid in the blisters does not contain urushiol and cannot spread the rash. However, if you have urushiol oil on your hands and touch other parts of your body, you can spread the oil and cause new rashes.