Red Blood Cell membrane element analysis. Blood and urine amino acid analyses, are helpful in determining amino acid deficiencies that sometimes correct symptoms. Intestinal permeability assays have already been mentioned. Red Blood Cell Fatty acid analyses have already been mentioned. Oxidative Stress analysis can help guide the reduction of free radicals produced by the Crohn's inflammation.
Herbs can help.
Slippery elm can calm and coat the intestine. Aloe vera juice is often quite helpful. White willow bark can reduce inflammation. Echinacea and Goldenseal can help to re-set the immune system. Other vitamin supplementation is important.