Suggest Treatment For Hives And Joint Pain

My daughter has been diagnosed with Fibro and Chronic Mono some time ago. We continually work to keep her healthy and feeling well. Most of the time she's ok. Lately she has been getting hives in randome places on her body. Many times they will appear in a joint (elbow or behind knee, wrist etc) after the hives go away her joints hurt so badly she can barely bend them. There seems to be no rhyme or reason for the hives. We've tracked food and things and can find no clue. She was bitten by a tick over the summer and she had a Lymes test which was negative, but I'm wondering if that could still be the culprit. She's always been achy but a lot more so now and the hives started about a month ago. Thank you for any help you can give.