Suggest Treatment For Red Itchy Bumps All Over The Body

My boyfriend randomly started getting red really itchy bumps (like misquito bites) all over his body last night. We thought it was an allergic reaction. Nothing has changed in his habits ect.. Now tonight those little bumps are huge swollen and hurting. He cant close his hand because it is really swollen . His hand is now 3 times the size as the other one. This has only started on his hand so far. Were waiting to see if it will go in the other areas were he has the other red lumps