How do you tell if you have sun poisoning?

i was walking the track on Saturday for relay for life i got really sun burnt on my arms and it hurts really bad and it itches it never itches when i usually get burned and it has never hurt this bad it usually it starts pealing the day after i get burned but it hasn't pealed yet and it hurts when i move so how do i tell if its just a bad burn or sun poisoning?