If the patient history indicates a non-IgE-mediated food allergy, or if IgE tests are inconclusive, then the dietary method is the most reliable way of diagnosing food allergy. The food allergy diagnosis is then made by the Elimination-Challenge Test. It is a dietary method that consists of an elimination (or exclusion) phase and a challenge phase. This should demonstrate:

• the relief of symptoms with the removal of cow milk, in case of cow milk allergy or of another food from the diet
• the recurrence of symptoms when cow milk is re-introduced during the challenge phase.

In the elimination phase, the clinician attempts to remove the harmful food antigen and assesses whether patient’s food allergy symptoms improve. This procedure requires the exclusion of the suspected foods and the maintenance of a diet free from all forms of the offending food, to avoid.
The amelioration of symptoms during dietary elimination of suspected foods provides presumptive evidence of a relation between these foods and the food allergy.

For allergic children, elimination diets can take several forms. In particular it can be done:

• by the lactating mother - breastfed infants may suffer allergic reactions to food antigen found in the mother’s diet (small quantaties also found in the breast milk) so in this case control of allergic symptoms and normal growth cannot be achieved. Therefore, prolonged breastfeeding is not recommended and instead infants should start feeding on hypoallergenic formulas;
  
  
• by the young bottle-fed infants - through the use of a validated hypoallergenic infant formula;
  
  
• by weaning older infants and children - in this case, it is important when weaning to avoid offending foods and introduce solid foods in the diet by selecting the least allergenic foods first

Elimination diets can be difficult, expensive and restrictive. A qualified dietician is required to supervise and ensure the diet is nutritionally adequate.