Poison Ivy. Hotness In Chest, Stomach Area After Taking Prednisone, Underweight. What Could Be The Reason?

Hello, My 10, almost 11-year-old son, was on prednisone recently for a very bad case of poison ivy. During the time he was on it, he was be very hot, particularly in his chest and stomach area. He would almost feel sick he was so hot. He has been off the prednisone for about a month and it got better but he is experiencing it again. He uses a cold pack from the freezer to cool down his stomach. He is not overweight . He is actually extremely underweight , so I don t feel it would be due to his weight. He has the air conditioner on in his room and he is still hot. He tends to be hot like this in bed. I even wondered if it could be puberty . I came across this site and figured I ask before I took the step of contacting his doctor. Maybe it s nothing to worry about. Thank you for your response.