He may be suffering from infectious mononucleosis. He would need testing to determine whether this is the case. It is a simple blood test that's done. I had no idea last winter, why I felt so tired all the time and seemed to be having more than my share of allergy problems. The dr. finally tested me and it was mono. I am still trying to get over the extreme tiredness I seem to feel all the time. I'll pray you get an answer.