My child has a bad case of eczema. I have tried lots of things but nothing seems to work for long?

Think prevention. Topical medications may help reduce or eliminate the rash of eczema temporarily, but the rash will come back. However, if your child is allergic to a food and it is avoided, that may help decrease the chances of the rash returning. Also, patients with eczema must continue gentle skin care and daily moisturizing for life to help prevent and severe dry cracking skin.
Ever see a doctor? In addition to regular use of gentle cleansers and good moisturizers (both fragrance-free), there are several prescription products that can help. Sometimes an oral antihistamine, like loratadine, cetirizine, fexofenadine, or Diphenhydramine can help. Eczema-prone skin seems to get infected more easily than you'd expect, so, sometimes a course of oral antibiotic can help with severe eczema.