Allergic reaction? What could all this itching be from ?

My 12 month old has been scratching herself nonstop for the past few weeks. She'll scratch her belly, hands, diaper area, and anywhere else she can reach. What could this mean ? I told her pedi and they said maybe eczema. She does have a rough patch of skin on her stomach but that's it's. They asked me to bring back her poop so it can be examined but meanwhile what could this be ?