This study involves investigating the effects of a pseudoallergen-free (active) diet compared with a control (placebo) diet in the treatment of Chronic Idiopathic Urticaria (CIU) and/or Angioedema. The hypothesis is that over a four-week intervention period, the pseudoallergen-free diet will be more effective than the placebo diet in reducing the frequency and severity of CIU and/or Angioedema.