Are there any dermatologists here?

I need some advice for my sister. She has this terrible rash that the doctor said was spring fever but I’m not so sure 

I wonder what the doctor meant by "Spring fever",as this is not a proper diagnosis. Was she given any treatment? Are you able to attach a photo?   Did it start suddenly or has it been building up gradually?   Is it a blistering rash or flat and red?   Where on her body? How old is your sister?

I think the proper name for it is Pityriasis rosea. It started off a small patch but now it’s all over her. She’s 25. Apparently the only thing she can take is antihistamines but they’re not working. 

Was hoping someone might know of another remedy to sooth the itching