My Friends 13 Yr Old Daughter Had Swim Team Practice

My friends 13 yr old daughter had swim team practice for 2 days then had a low grade fever 99.9 with puffy hands. Hives started the next day on her back, arms and butt. She feels better 3rd day out but the hives return when the benedryl she is taking wears off. The hives itch and are hot. She hasn't Been back to swim practice. Any thoughts or suggestions for treatment? Thank you.