K.B.
It's so tough. My daughter also had really bad excema, brought on by food allergies. We brought her to both a dermatologist and allergist and have gotten it under control. The recommendations we got from both: Give her a bath every night. Use Cetaphil cleanser. Immediately after her bath while her skin is still moist, lather her up with Vaseline or Hydrolatum good and thick. you can use the hydrocortisone first and then the vaseline overtop--which will seal it in. If any areas are open, you should ask pedi about antibiotic cream since my daughter often had a staph infection as a result. If she's scratching, use socks to cover her hands.
One note--the vaseline stains clothing--so I always did it under PJs and the Hydrolatum in the AM since it didn't seem to doing anything to clothes.
Good luck. It's very stressful.