It can be due to a viral infection, hives due to viral infection , allergic reaction or pityriasis rosea. Pityriasis rosea is a common human skin disease which presents as numerous patches of pink or red oval rash. The rash may be accompanied by low-grade headache, fever, nausea and fatigue and sometimes by itching.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
My 2 yr old daughter had the exact thing. We found out she was allergic to dairy/milk products. Once we eliminated dairy the itchy rashes went away. If she so much as has just a few crackers with whey in them she will get a few itchy bumps on her belly again. I would maybe get her tested for food allergies and dont them them talk you out of testing, its your child who is suffering.