In the diagnosis of food allergies, CRD is particularly useful because it allows: (i) to detect the patient’s profile of sensitization; (ii) to quantify specific IgE (and, therefore, predict symptom severity), (iii) to verify the possibility of cross-reactions (IgE reactions with highly similar allergens from different sources), and (iv) to identify patients with low levels of specific IgE, who could be subjected to immunotherapy protocols. The gene discussed is IGHE; the disease is food allergy.