Can A Spider Bite Causes Rashes On Back And Arms?

my son has 3 rash looking marks on his back and one on his arm. he says they are very itchy. they're not raised a lot. could it be bed bugs or a spider bite? they look very irritated and i tried looking closely to see if i could find the spot where he was bitten in the middle of these and i cant seem to see one but i know he got bit by something and this isnt the first time