My Granddaughter That Is 8 Years Old Had The Skin

My granddaughter that is 8 years old had the skin on her arms from her shoulders to her elbows start itching. Then they turned red like a sunburn. Her stomach had red spots come up and they were itchy as well. I took her to the clinic. The Dr on called said it was an allergic reaction to something. He told me to give her Benadryl. It helped a little. But today it's still there and it doesn't look like it's getting better. I tried different creams and even the aloe Vera plant. It started stinging.
The skin looks cracked and dry and is painful.
Do you have any idea what it could be?
Thank you
Patricia