Strange symptoms for a 2 1/2 yr old?

My 2 1/2 yr old has what looks like white hives on his knuckles..and fingers. only on the backside of his hands....last thurs/fri he was sick with diarhea, and vomiting...NO FEVER. playing fairly normally, just complaing that his hands hurt. these 'mosquito' like bumps went away after about 1 1/2 hr. They aren't poison ivy or bug bites...raynauds? a virus? how can i bring him to dr if the symptoms are gone?