I don't know what it could be as far as treatment. One thing that comes to mind though is it's not from CORN which is a big eczema trigger. I use coconut oil. A diet rich in omega fats is good for eczema, like fish oil, flax oil etc.
As well as keeping away from any food triggers. It doesn't mean there's an "allergy" exactly, but certain foods can be a trigger for the skin. I keep DD away from corn, eggs, strawberries, cucumbers and some nuts. She can have a little of one on one day, but not too much and not if she's alreayd dealing with seasonal allergies. You have to figure out what triggers the rash and keep away from it.
Warm soothing bathes and a good rub down with coconut oil is good too