My son 8 years old has hive like rash on his arms and leg now on torso. I give him benedryl and it goes away and re-appears when the benedryl wears off. He has been allergic to dogs, milk soy and eggs but has not been in contact with any of those. He has no ever but is tired and was tonight a bit dizzy. We just got back from a trip to Barbados ( for a week) could this be not hives could this be a virus? If so what type of virus would cause this rash that looks and is itchy like hives for two days and no fever?