hi.  this seriously sounds just like hives.  occurs at night then is gone next day?  thats what i get.  some people just get hives for no real reason.  they just get them.  i think thats me.  although, there are about a million things that could cause hives.  i just use benadryl cream and take Singulair.  also, sometimes rubbing alcohol helps as its very soothing to the skin.  and ive read somewhere on the net that Vicks works?  (not sure about that one, but you can easily research it).   hope that helped.   also, the other ones im reading about here, sounds like bed bugs or scabies.  most doctors are not "hip" on bedbugs and dont usually diagnose it, but scabies is easily tested for.