What is this on his skin?

My boyfriend has little blisters all over his hands which seem to be under the skin and they are red. He also has a few big blisters on his feet and had one little on one his inner lip. He has been feeling very weak and had a fever, but it's gone now. He has a lose of appetite, sore throat, headaches, dizzy when standing and is dehydrated. The blisters burn when he has them in water and they are very painful when he is putting pressure on them. What could this be?