13 month old baby with blistery rash no itch or fever only on arms legs &face not on trunk?

Brought him to doctor who then suggested hospital so brought him there and they said it was viral but rash had almost gone by the time doctor in hospital seen him. Next day it came out again worse so brought him back to hospital as there was what looked like a blister the size of a 20cent coin next to his eye. They reckon it is either an allergic reaction or viral and gave him steroids & antihystamines. Have not changed anything in his diet or washing powder. This rash disappears almost completely and then reappears has anyone ever experienced this??