My Daughter Has Recently Been Diagnosed With GERD. Three Days

My daughter has recently been diagnosed with GERD. Three days after starting proton pump inhibitors she developed severe rashes. The doctor switched her to an H2 blocker but that is not providing relief and she is in graet pain. What should we do? Endoscopy and CT scan were clean and she is not having any obvious food that cause acid reflux...just having apple and yogurt