Hi Ange --
Eczema is usually an allergy/sensitivity to something. Often it's laundry detergent or fabric softener. Although it can be triggered by a food. I encourage you to check out the book "Is This My Child?" by Dr. Doris Rapp. She has excellent advice on what may be triggering your childs eczema.
As for treating the symptoms. A topical creme will give temporary results, but for long term results, finding the trigger is the real solution.
Start by switching your laundry products. Choose an Eco Friendly green brand, preferrably w/o fragrance. As for fabric softener, choose a fragrance free green dryer sheet. Also choose non-toxic cleaners to clean the bathtub and for handwashing, choose one that's Triclosan free.
If you get no results with these changes, I suggest you look into the Feingold diet. Many clients find it very helpful.
Best of health,
S.