Talk to Dermatologist on Atopic Dermatitis Ezcema

My son have atopic dermatitis since he was 1 month now he is 4 years old. Before it use to be on neck leg or arm folding. Now for past 4 months it have flared up a lot on his whole body including face and around eyes. I keep him moisturized always still the issue is not settling down unless i apply steroids. I need to know what all tests i can conduct to know the cause or any other recommendations i can follow.