Jarom and allergic reaction to the unknown

A couple nights Jarom came upstairs with his shirt off and I was shocked. He was covered in hives from head to toe... worse breakout than anything I had ever seen! I ended up taking him to Park City to a Dr. by then half the hives wore gone. With no idea of what went on... then the next morning he went outside and broke out with in a few minutes... this was a picture of his upper back. But we haven't seen him broke out since. CRAZY!