What could this be from?

My son only has this on his legs. He is 20 months old. He doesn’t really have dairy. He eats a lot of bananas. Last week we tried tofu with him for the first time. He’s well in himself and producing nappies etc. I bath him everyday and I change the bedsheets every week. I moisturise him with coconut oil. (Yes I’m waiting for appointment but have been let down by gps in the past so wanted to see if other mums went through this.)